Thrombin signalling and protease-activated receptors

Attenuation of Atherosclerosis With PAR4 Deficiency: A Potential Role of Hematopoietically Expressed PAR4 in Atherosclerosis

BACKGROUND

Cardiovascular disease is a significant burden globally and, despite current therapeutics, remains the leading cause of death. PAR (protease-activated receptor) 4 is a receptor highly expressed by hematopoietic cells, strongly activated by thrombin, and plays a vital role in platelet activation and aggregation. However, the role of PAR4 in atherothrombotic disease remains understudied.

METHODS

Mice on a low-density lipoprotein receptor-deficient (Ldlr-/-) background were bred with Par4-deficient (Par4-/-) mice to create Ldlr-/-/Par4+/+ and Ldlr-/-/Par4-/- cousin lines. Mice were fed high-fat (42%) and high-cholesterol (0.2%) Western diet for 12 weeks for all studies. Bone marrow transplant studies were conducted by irradiating Ldlr-/-/Par4+/+ and Ldlr-/-/Par4-/- mice with 550 rads (2×, 4 hours apart) and then repopulated with Par4+/+ or Par4-/- bone marrow. To determine whether the effects of thrombin were mediated solely by PAR4, the thrombin inhibitor dabigatran was added to the Western diet.

RESULTS

We observed higher abundance of PAR4 in arteries with atherosclerosis in mouse and human lesions versus healthy controls. Using a global deletion of PAR4, we observed an attenuation in atherosclerosis versus Par4+/+ mice. Bone marrow transplant studies demonstrated these effects were due to hematopoietic cells. When observing whether PAR4 activation via thrombin contributes to atherosclerotic development, Ldlr-/-/Par4-/- mice given dabigatran did not further decrease their atherosclerotic burden. Differences between apoE-deficient (apoE-/-) and Ldlr-/- platelets were assessed for changes in reactivity. PAR4 appeared to be acting independent of PAR1, as there were no changes with the addition of dabigatran to Par4-/- mice. apoE-/- platelets were hyperreactive compared with Ldlr-/- platelets.

CONCLUSIONS

We conclude that hematopoietic-derived PAR4 plays a vital role in the development and progression of atherosclerosis. More specifically, we observe thrombin-activated PAR4 contributes to the progression. Specifically, targeting of PAR4 may be a potential therapeutic target for cardiovascular disease.

Protein C in adult patients with sepsis: from pathophysiology to monitoring and supplementation

Protein C (PC) plays a crucial role in modulating inflammation and coagulation in sepsis. Its anticoagulant and cytoprotective properties are critical in mitigating sepsis-induced coagulopathy, which is associated with high mortality rates. In sepsis, low levels of PC are associated with an elevated risk of multiple organ dysfunction and increased mortality. Routine monitoring of PC levels is not widely implemented but appears relevant in selected populations, such as patients with purpura fulminans, sepsis-induced coagulopathy (SIC), disseminated intravascular coagulopathy (DIC) or hyperinflammatory septic shock phenotypes. Treatment with PC has been limited to PC concentrate approved for paediatric use in congenital PC deficiencies and purpura fulminans, while the efficacy of PC supplementation in sepsis remains a subject of debate. Considering the physiological significance of PC and its role in sepsis pathophysiology, additional studies are necessary to fully elucidate its therapeutic efficacy in specific clinical settings.

Mice with reduced protease-activated receptor 4 reactivity show decreased venous thrombosis and platelet procoagulant activity

BACKGROUND

Hypercoagulation and thrombin generation are major risk factors for venous thrombosis. Sustained thrombin signaling through protease-activated receptor (PAR) 4 promotes platelet activation, phosphatidylserine exposure, and subsequent thrombin generation. A single nucleotide polymorphism in PAR4 (rs2227376) changes proline to leucine extracellular loop 3, which decreases PAR4 reactivity and is associated with a lower risk for venous thromboembolism (VTE) in a genome wide association studies meta-analysis.

OBJECTIVES

The goal of this study was to determine the mechanism for the association of rs2227376 with a reduced risk of VTE using mice with a homologous mutation (PAR4-P322L).

METHODS

Venous thrombosis was examined using our recently generated PAR4-P322L mice in the inferior vena cava stasis and stenosis models. Coagulation and clot stability were measured using rotational thromboelastometry. Thrombin-generating potential was measured in platelet-rich plasma. Phosphatidylserine surface expression and platelet-neutrophil aggregates were analyzed using flow cytometry.

RESULTS

Mice heterozygous (PAR4P/L) or homozygous (PAR4L/L) at position 310 had reduced sizes of venous clots at 48 hours. PAR4P/L and PAR4L/L platelets had progressively decreased phosphatidylserine in response to thrombin and convulxin, in addition to decreased thrombin generation and decreased PAR4-mediated platelet-neutrophil aggregation.

CONCLUSION

The leucine allele in extracellular loop 3, PAR4-322L, leads to fewer procoagulant platelets, decreased endogenous thrombin potential, and reduced platelet-neutrophil aggregation. This decreased ability to generate thrombin and bind to neutrophils offers a mechanism for PAR4's role in VTE, highlighting a key role for PAR4 signaling.

Receptors and host factors: key players in human metapneumovirus infection

Human metapneumovirus (hMPV) is a significant global pathogen that causes acute respiratory tract infections, especially in infants, young children, the elderly, and immunocompromised individuals. Despite its increasing prevalence, there are currently no vaccines or effective treatments available for hMPV. The pathogenesis of hMPV infection is a complex process involving a multitude of host factors and viral receptors. These interactions determine the virus ability to enter host cells, replicate, and evade the immune response. This review is the first to provide a comprehensive overview of the current understanding of host-virus interactions in hMPV pathogenesis. By elucidating these mechanisms, we can identify potential targets for antiviral drugs and improve the management of hMPV infections.

Precise Identification of Inhibitors for Coagulation Reactions from Complex Extracts through Monitoring of Biological Aggregates Combined with a Targeted Fishing Technique

Biological aggregates play a crucial role in the pathogenesis of thrombotic diseases, especially thrombin-induced biological aggregates. Therefore, the efficient discovery of thrombin inhibitors is of great significance for the prevention and treatment of thrombotic diseases. In this study, the aggregation precursor protein fluorescent probe was successfully prepared for monitoring the production of biological aggregates induced by thrombin. In this program, the aggregation degree of biomolecules can be quickly monitored through a fluorescence sensing technology. To facilitate the modulation of the biological aggregation process, the application of this advanced fluorescence sensing technology was utilized for the screening of thrombin inhibitors, which are pivotal regulatory molecules in biological aggregation. In addition, by combining the target fishing technique, an integrated model for rapid screening of potential inhibitors in complex extracts was further established. This model not only swiftly detects the presence of inhibitory components within complex systems but also precisely captures and identifies active monomers. After positive drug validation of the screening model, three active monomers, namely, ginkgetin, isoginkgetin, and bilobetin, were accurately screened from 30 natural products. These results highlighted the immense potential of the proposed approach for screening active ingredients from a wide range of natural products.

PAR2 Serves an Indispensable Role in Controlling PAR4 Oncogenicity: The β-Catenin-p53 Axis

Although the role of G-protein-coupled receptors (GPCRs) in cancer is acknowledged, GPCR-based cancer therapy is rare. Mammalian protease-activated receptors (PARs), a sub-group of GPCRs, comprise four family members, termed PAR1-4. Here, we demonstrate that PAR2 is dominant over PAR4 oncogene in cancer. We performed a knockdown of Par2/f2rl1 and expressed C-terminally truncated PAR2 (TrPAR2), incapable of inducing signaling, to assess the impact of PAR2 on PAR4 oncogenic function by β-catenin stabilization assessment, immunoprecipitation, and xenograft tumor generation in Nude/Nude mice. PAR2 and PAR4 act together to promote tumor generation. Knockdown Par2 and TrPAR2 inhibited the PAR2 and PAR4-induced β-catenin levels, nuclear dishevelled 1(DVL1), and TOPflash reporter activity. Likewise, PAR2 and PAR4-induced invasion and migration were inhibited when Par2 was knocked down or in the presence of TrPAR2. PAR cyclic (4-4) [Pc(4-4)], a PAR-based compound directed toward the PAR pleckstrin homology (PH)-binding site, effectively inhibited PAR2 oncogenic activity. Pc(4-4) inhibition is mediated via the increase in p53 level and the up-regulation of p21 as caspase-3 as well. Overall, we showed that in the absence of PAR2 signaling, the PAR4 pro-tumor functions are significantly inhibited. Pc(4-4) inhibits PAR2 acting via the modification of wt p53, thus offering a powerful drug measure for fighting cancer.

Defect in Sensing Human Thrombin by Porcine Endothelial Protease-Activated Receptor-1: Molecular Incompatibility Between Porcine PAR-1 and Human Thrombin

Xenotransplantation, the transplantation of organs from pigs to humans, presents significant challenges due to immune rejection, which is driven by molecular incompatibilities between species. This study investigates the compatibility between human thrombin and porcine protease-activated receptor-1 (PAR-1), a key regulator of both coagulation and inflammatory responses. Human thrombin activates PAR-1 in human vascular endothelial cells, but our results demonstrate that human thrombin does not effectively activate PAR-1 in porcine vascular endothelial cells due to differences in amino acid sequences, particularly at the thrombin cleavage site and the Hir domain. Protein-protein docking analysis further reveals that porcine PAR-1 forms less stable interactions with human thrombin compared to human PAR-1, resulting in reduced activation. This molecular incompatibility likely contributes to impaired nitric oxide (NO) production, endothelial dysfunction, and increased inflammation, which are critical for the survival of transplanted organs. Additionally, experiments using the PAR-1 inhibitor vorapaxar (Vor) show that inhibiting PAR-1 signaling can suppress inflammatory cytokine and chemokine expression in co-cultures of human macrophages and porcine endothelial cells. These findings suggest that selective PAR-1 inhibitors or targeted therapies regulating thrombin-PAR-1 signaling may improve the success rate of xenotransplantation. However, further in vivo studies are needed to validate these findings and explore therapeutic interventions targeting thrombin-PAR-1 interactions to enhance xenograft survival.

Deficiency of neutrophil gelatinase-associated lipocalin elicits a hemophilia-like bleeding and clotting disorder in mice

ABSTRACT

Coagulation is related to inflammation, but the key pathway, especially innate immune system and coagulation regulation, is not well understood and need to be further explored. Here, we demonstrated that neutrophil gelatinase-associated lipocalin (NGAL), an innate immune inflammatory mediator, is upregulated in patients with thrombosis. Furthermore, it contributes to the initiation and amplification of coagulation, hemostasis, and thrombosis. This occurs by enhancing tissue factor expression on the cell surface, potentiating various clotting factors such as thrombin, kallikrein, factor XIa (FXIa), and FVIIa, promoting thrombin-induced platelet aggregation, and inhibiting antithrombin. NGAL knockout led to strikingly prolonged clot reaction time and kinetic time in thromboelastography analysis, along with reduced thrombus generation angle and lower thrombus maximum amplitude, which were in line with remarkably prolonged activated partial thromboplastin time and prothrombin time. In several mouse hemostasis and thrombosis models, NGAL overexpression or IV administration promoted coagulation and hemostasis and aggravated thrombosis, whereas NGAL knockout or treatment with anti-NGAL monoclonal antibody significantly prolonged bleeding time and alleviated thrombus formation. Notably, NGAL knockout prolonged mouse tail bleeding time or artery occlusion time to over 40 or 60 minutes, respectively, resembling uncontrollable bleeding and clotting disorder seen in hemophilic mice. Furthermore, anti-NGAL monoclonal antibody treatment markedly reduced the formation of blood clots in inflammation-induced thrombosis models. Collectively, these findings unveil a previously unidentified role of NGAL in the processes of coagulation, hemostasis, and thrombosis, as well as the cross talk between innate immunity, inflammation, and coagulation. Thus, modulating NGAL levels could potentially help balance thrombotic and hemorrhagic risks.

Anti-fibrotic effects of thrombin inhibition in systemic sclerosis-associated interstitial lung disease: Proof of concept

Introduction

Activation of the coagulation cascade leading to generation of thrombin is well documented in various forms of lung injury including systemic sclerosis-associated interstitial lung disease (SSc-ILD). We previously demonstrated that the direct thrombin inhibitor dabigatran inhibits thrombin-induced profibrotic signaling in lung fibroblasts isolated from scleroderma patients. The objective of this study was to characterize and compare lung fibroblasts from an SSc-ILD patient at baseline and after dabigatran treatment to ascertain this therapy's differential effects on fibrogenic gene expression.

Materials and methods

Lung fibroblasts isolated by bronchoalveolar lavage (BAL) from a SSc-ILD patient before and after receiving dabigatran (Pradaxa®) 75 mg twice daily for 6 months (ClinicalTrials.gov Identifier NCT02426229) were analyzed by RNA sequencing, real-time quantitative reverse transcription polymerase chain reaction (qRT)-PCR, and immunofluorescent staining.

Results

Thrombin inhibition for six-months by oral dabigatran resulted in significantly decreased expression of 708 lung fibroblast genes as compared to basal levels before dabigatran treatment. Using Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, we determined that thrombin-inhibition by dabigatran primarily affected extracellular matrix (ECM) and ECM-related genes. Fibrosis-associated genes, including smooth muscle alpha-actin (SMA, ACTA2), tenascin C, collagen 1 alpha 1 (COL1A1), collagen 3 alpha1 (COL3A1), collagen 8 alpha 2 (COL8A2), collagen 10 alpha 1 (COL10A1), collagen 5 alpha 1 (COL5A1), fibronectin 1, connective tissue growth factor (CTGF), and procollagen-lysine-2-oxoglutarate-5-dioxygenase-2 (PLOD2) were all significantly down regulated following thrombin inhibition by dabigatran treatment. Real-time qRT-PCR and immunofluorescent staining confirmed significant downregulation of the selected genes at the mRNA and protein levels.

Conclusion

Inhibition of thrombin in this SSc-ILD patient treated with low-dose dabigatran etexilate downregulated profibrotic proteins in lung fibroblasts, providing further support for the use of thrombin inhibitors as a therapeutic approach for the treatment of patients with SSc-ILD.

Activation of the Coagulation Cascade as a Universal Danger Sign

Hemostasis is a mechanism that stops bleeding from an injured vessel, involves multiple interlinked steps, culminating in the formation of a "clot" sealing the damaged area. Moreover, it has long been recognized that inflammation also provokes the activation of the coagulation system. However, there has been an increasing amount of evidence revealing the immune function of the hemostasis system. This review collects and analyzes the results of the experimental studies and data from clinical observations confirming the inflammatory function of hemostasis. Here, we summarize the latest knowledge of the pathways in immune system activation under the influence of coagulation factors. The data analyzed allow us to consider the components of hemostasis as receptors recognizing «foreign» or damaged «self» or/and as «self» damage signals that initiate and reinforce inflammation and affect the direction of the adaptive immune response. To sum up, the findings collected in the review allow us to classify the coagulation factors, such as Damage-Associated Molecular Patterns that break down the conventional concepts of the coagulation system.

Activation of PAR1 contributes to ferroptosis of Schwann cells and inhibits regeneration of myelin sheath after sciatic nerve crush injury in rats via Hippo-YAP/ACSL4 pathway

OBJECTIVE

Peripheral nerve injury (PNI) is characterized by high incidence and sequela rate. Recently, there was increasing evidence that has shown ferroptosis may impede functional recovery. Our objective is to explore the novel mechanism that regulates ferroptosis after PNI.

METHODS

LC-MS/MS proteomics was used to explore the possible differential signals, while PCR array was performed to investigate the differential factors. Besides, we also tried to activate or inhibit the key factors and then observe the level of ferroptosis. Regeneration of myelin sheath was finally examined in vivo via transmission electron microscopy.

RESULTS

Proteomics analysis suggested coagulation signal was activated after sciatic nerve crush injury, in which high expression of F2 (encoding thrombin) and F2r (encoding PAR1) were observed. Both thrombin and PAR1-targeted activator TRAP6 can induce ferroptosis in RSC96 cells, which can be rescued by Vorapaxar (PAR1 targeted inhibitor) in vitro. Further PCR array revealed that activation of PAR1 induced ferroptosis in RSC96 cells by increasing expression of YAP and ACSL4. Immunofluorescence of sciatic nerve confirmed that the expression of YAP and ACSL4 were simultaneously reduced after PAR1 inhibition, which may contribute to myelin regeneration after injury in SD rats.

CONCLUSION

Inhibition of PAR1 can relieve ferroptosis after sciatic nerve crush injury in SD rats through Hippo-YAP/ACSL4 pathway, thereby regulating myelin regeneration after injury. In summary, PAR1/Hippo-YAP/ACSL4 pathway may be a promising therapeutic target for promoting functional recovery post-sciatic crush injury.

Integrative phosphoproteomic analyses reveal hemostatic-endothelial signaling interplay

BACKGROUND

The vascular endothelial cell (EC) monolayer plays a crucial part in maintaining hemostasis. An extensive array of G protein-coupled receptors allows ECs to dynamically act on key hemostatic stimuli such as thrombin and histamine. The impact of these individual stimuli on EC signal transduction has been the subject of various studies, but insight into discordant and concordant EC signaling between different G protein-coupled receptors remains limited.

OBJECTIVES

To elucidate histamine and protease-activated receptor (PAR1-4) signaling cascades in ECs, discern overlapping and diverging regulation between these stimuli and their effect on the EC monolayer.

METHODS

We employed stable isotope labeling by amino acids in cell culture mass spectrometry-based phosphoproteomics on in vitro cultured blood outgrowth ECs stimulated with histamine and different PAR1 to 4 peptides. We investigated key phosphosites through immuno(fluorescence) staining and determined effects on barrier function through transendothelial resistance assays.

RESULTS

EC histamine activation initiated an extensive (kinase) signaling network (including MAPK3, STAT3, and CTNND1). PAR1 and PAR2 receptors induced highly similar signaling cascades, whereas PAR3 and PAR4 induced minimal phospho-regulation. Integration of all applied stimuli indicated uniquely activated proteins between both stimuli, as well as a general overlapping activation of cell junction and actin cytoskeletal proteins.

CONCLUSION

We provide an integrative phosphoproteomic analysis of histamine and PAR agonists in the endothelium that highlights the endothelial response programs that are at the basis of regulating hemostasis.

CARD9 deficiency alleviates septic pulmonary embolism

Purpose: Dysfunction of pulmonary microvascular endothelial cells (PMVECs) is an important feature of pulmonary embolism (PE) in sepsis. This study aimed to explore the impact of caspase recruitment domain-containing protein 9 (CARD9) on sepsis-induced PE. Materials and Methods: Proteomic analysis was performed on serum of sepsis patients with PE to identify differentially expressed proteins. Wild-type (WT) and CARD9 knockout (KO) mice were used to establish PE in sepsis mouse model. In vitro and in vivo sepsis models were established to evaluate PMVEC function. Tiliroside (TIS) was tested for its therapeutic effects via modulation of the CARD9-mediated MAPK/NF-κB pathway. Results: In the pulmonary vascular endothelial tissues of mice with sepsis, a total of 46 proteins exhibited differential expression, and CARD9 was one of the changes proteins. Both CARD9 knockout (KO) and silencing were found to effectively ameliorate sepsis-induced dysfunction of PMVECs in both in vivo and in vitro models of sepsis. Tiliroside (TIS), an active constituent derived from Buddleja officinalis Maxim, demonstrated a significant capacity to enhance the function of PMVECs in sepsis by modulating the CARD9-mediated MAPK/NF-κB signaling pathway. Conclusion: In summary, CARD9 emerges as a potential molecular target for the treatment of sepsis-associated PE dysfunction.

Protease-activated receptors in vascular smooth muscle cells: a bridge between thrombo-inflammation and vascular remodelling

Coagulation factors are responsible for blood clot formation yet have also non-canonical functions as signalling molecules. In this context, they can activate protease-activated receptors (PARs) ubiquitously expressed in the vasculature. During vascular repair, vascular smooth muscle cells (VSMCs) will switch from a contractile to a synthetic reparative phenotype. During prolonged vascular stress, VSMCs acquire a pathological phenotype leading to cardiovascular disease. Activated coagulation factors impact on vessel wall permeability and integrity after vascular injury with a key role for PAR activation on endothelial cells. The activation of PARs on VSMCs supports vessel wall repair following injury. Prolonged PAR activation, however, results in pathological vascular remodelling. Therefore, understanding the mechanisms of PAR activation on VSMCs is key to propel our understanding of the molecular and cellular mechanisms to develop novel therapeutic strategies to resolve vascular remodelling.In this review, we discuss recent advances on the role of PAR signalling on VSMCs and specifically their role in vascular remodelling contributing to cardiovascular disease. Additionally, we discuss current therapeutic strategies targeting PAR signalling - indirectly or directly - in relation to cardiovascular disease.

Nicotine's impact on platelet function: insights into hemostasis mechanisms

Introduction

Traditional Miao and Dai Chinese medicines have used nicotine-rich leaf tobacco to treat traumatic injuries by promoting hemostasis. While nicotine is known to enhance platelet aggregation, its effects on other platelet functions and underlying mechanisms remain unclear.

Methods and Results

This study aimed to thoroughly investigate nicotine's effects on human platelets and its pharmacological mechanisms, using thromboelastography to assess nicotine's impact on platelet function during coagulation. This study aimed to investigate the functional effects of nicotine on human platelets and elucidate its pharmacological mechanisms. The impact of nicotine on platelet function during the coagulation process was assessed using thromboelastography. Further studies showed that nicotine fully activates washed platelets, promoting aggregation, granule release, adhesion, spreading, and plaque retraction. Concurrently, nicotine was found to enhance the intracellular concentration of calcium ions in platelets ([Ca2+]i). To explore the underlying mechanisms, molecular docking software was employed to identify the platelet membrane receptors PAR1 and PAR4, which exhibited the highest docking scores with nicotine. Intervention with two receptor inhibitors demonstrated that only the PAR4 inhibitor could reverse the stimulatory effects of nicotine on platelet granule release. Through the examination of alterations in the downstream signaling pathways of PAR4 receptors, it was determined that nicotine promo-facilitates the phosphorylation of PI3K, AKT, and ERK1/2 proteins, subsequently contributing to the activation of αIIbβ3 receptors in platelets. Conversely, the application of PAR4 inhibitors was found to reverse these effects.

Discussion

In conclusion, nicotine activates αIIbβ3 receptors and significantly enhances platelet function by promoting the phosphorylation of the platelet PAR4 receptor signaling pathway. These findings suggest the potential utility of nicotine as a hemostatic agent.

Discovery of quinazoline-benzothiazole derivatives as novel potent protease-activated receptor 4 antagonists with improved pharmacokinetics and low bleeding liability

Protease-activated receptor 4 (PAR4) plays a critical role in the development of pathological thrombosis, and targeting PAR4 is considered a promising strategy for improving antiplatelet therapies. Here, we reported the design of a series of quinazoline-benzothiazole-based PAR4 antagonists using a scaffold-hopping strategy. Systematic structure-activity relationship exploration leads to the discovery of compounds 20f and 20g, which displayed optimal activity (h. PAR4-AP PRP IC50 = 6.39 nM and 3.45 nM, respectively) on human platelets and high selectivity for PAR4. Both of them also showed excellent metabolic stability in human liver microsomes (compound 20f, T1/2 = 249.83 min, compound 20g, T1/2 = 282.60 min) and favourable PK profiles in rats (compound 20f, T1/2 = 5.16 h, F = 50.5 %, compound 20g, T1/2 = 7.05 h, F = 27.3 %). More importantly, neither compound prolonged the bleeding time in the mouse tail-cutting model (10 mg/kg, p.o.). These results suggest that these compounds have great potential for use in antiplatelet therapies.

Protease-activated receptor 2 deficient mice develop less angiotensin II induced left ventricular hypertrophy but more cardiac fibrosis

AIMS

Activation of Protease Activated Receptor 2 (PAR2) has been shown to be involved in regulation of injury-related processes including inflammation, fibrosis and hypertrophy. In this study we will investigate the role of PAR2 in cardiac injury in a mouse model of hypertension using continuous infusion with angiotensin II.

METHODS

Hypertension was induced in 12 weeks old wildtype (wt, n = 8) and PAR2 deficient mice (n = 9) by continuous infusion with angiotensin II for 4 weeks using osmotic minipumps. At the end, hearts were collected for analysis of left ventricular hypertrophy (LVH), myocardial capillary supply, fibrosis and localization of PAR2 expression using histological, immunohistological and mRNA expression analysis techniques. In addition, rat cardiac fibroblasts were treated with angiotensin II and PAR2 was inhibited by a blocking antibody and the PAR2 inhibitor AZ3451.

RESULTS

Cardiac PAR2 mRNA expression was downregulated by 40±20% in wt mice treated with AngII compared to untreated controls. Four weeks after AngII treatment, LVH was significantly increased in AngII-treated wt mice compared to similarly treated PAR2-deficient animals as determined by relative heart weight, left ventricular cross-sectional area, and analysis of ventricular lumen area determined on sections. Treatment of wt mice resulted in an approximately 3-fold increase in cardiac expression of FGF23, which was 50% lower in PAR2-deficient animals compared to wt animals and therefore no longer significantly different from expression levels in untreated control mice. In contrast, cardiac interstitial fibrosis was significantly higher in PAR2-deficient mice compared to similar treated wt controls, as assessed by Sirius Red staining (>3-fold) and collagen IV staining (>2-fold). Additional experiments with isolated cardiac fibroblasts showed induction of pro-fibrotic genes when treated with PAR2 inhibitors.

CONCLUSION

In angiotensin II-induced cardiac injury, PAR2 deficiency has an ambivalent effect, enhancing fibrosis on the one hand, but reducing LVH on the other.

Glycocalyx disruption, endothelial dysfunction and vascular remodeling as underlying mechanisms and treatment targets of chronic venous disease

The glycocalyx is an essential structural and functional component of endothelial cells. Extensive hemodynamic changes cause endothelial glycocalyx disruption and vascular dysfunction, leading to multiple arterial and venous disorders. Chronic venous disease (CVD) is a common disorder of the lower extremities with major health and socio-economic implications, but complex pathophysiology. Genetic aberrations accentuated by environmental factors, behavioral tendencies, and hormonal disturbances promote venous reflux, valve incompetence, and venous blood stasis. Increased venous hydrostatic pressure and changes in shear-stress cause glycocalyx injury, endothelial dysfunction, secretion of adhesion molecules, leukocyte recruitment/activation, and release of cytokines, chemokines, and hypoxia-inducible factor, causing smooth muscle cell switch from contractile to synthetic proliferative phenotype, imbalance in matrix metalloproteinases (MMPs), degradation of collagen and elastin, and venous tissue remodeling, leading to venous dilation and varicose veins. In the advanced stages of CVD, leukocyte infiltration of the vein wall causes progressive inflammation, fibrosis, disruption of junctional proteins, accumulation of tissue metabolites and reactive oxygen and nitrogen species, and iron deposition, leading to skin changes and venous leg ulcer (VLU). CVD management includes compression stockings, venotonics, and surgical intervention. In addition to its antithrombotic and fibrinolytic properties, literature suggests sulodexide benefits in reducing inflammation, promoting VLU healing, improving endothelial function, exhibiting venotonic properties, and inhibiting MMP-9. Understanding the role of glycocalyx, endothelial dysfunction, and vascular remodeling should help delineate the underlying mechanisms and develop improved biomarkers and targeted therapy for CVD and VLU.

Rivaroxaban as a Protector of Oxidative Stress-Induced Vascular Endothelial Glycocalyx Damage via the IQGAP1/PAR1-2/PI3K/Akt Pathway

INTRODUCTION

The vascular endothelial glycocalyx, crucial for blood vessel integrity and homeostasis, is vulnerable to oxidative stress, leading to endothelial dysfunction, which strongly correlates with cardiovascular disease (CVD). This study investigates the protective effects of rivaroxaban, a factor X inhibitor, on the glycocalyx under oxidative stress condition.

METHODS

We examined the impact of rivaroxaban on human umbilical vein endothelial cells exposed to acute and chronic H2O2-induced oxidative stress.

RESULTS

Rivaroxaban dose-dependently suppressed syndecan-1, a key component of the glycocalyx, shedding from cell surface, and enhanced protease-activated receptor (PAR)1-PAR2/phosphatidylinositol-3-kinase (PI3K)-dependent cell viability after acute induction of H2O2. This protective effect was linked to the translocation of IQGAP1, a scaffold protein that modulates the actin cytoskeleton, to the perinucleus from the cell membrane. Under chronic H2O2 treatments, rivaroxaban improves cell viability accompanied by an increase in hyaluronidase activities, aiding the turnover and remodeling of hyaluronic acid within the glycocalyx.

CONCLUSION

We identify that rivaroxaban protects against oxidative stress-induced endothelial glycocalyx damage and cell viability through IQGAP1/PAR1-2/PI3K/Akt pathway, offering a potential to be a therapeutic target for CVD prevention.

INTRODUCTION

The vascular endothelial glycocalyx, crucial for blood vessel integrity and homeostasis, is vulnerable to oxidative stress, leading to endothelial dysfunction, which strongly correlates with cardiovascular disease (CVD). This study investigates the protective effects of rivaroxaban, a factor X inhibitor, on the glycocalyx under oxidative stress condition.

METHODS

We examined the impact of rivaroxaban on human umbilical vein endothelial cells exposed to acute and chronic H2O2-induced oxidative stress.

RESULTS

Rivaroxaban dose-dependently suppressed syndecan-1, a key component of the glycocalyx, shedding from cell surface, and enhanced protease-activated receptor (PAR)1-PAR2/phosphatidylinositol-3-kinase (PI3K)-dependent cell viability after acute induction of H2O2. This protective effect was linked to the translocation of IQGAP1, a scaffold protein that modulates the actin cytoskeleton, to the perinucleus from the cell membrane. Under chronic H2O2 treatments, rivaroxaban improves cell viability accompanied by an increase in hyaluronidase activities, aiding the turnover and remodeling of hyaluronic acid within the glycocalyx.

CONCLUSION

We identify that rivaroxaban protects against oxidative stress-induced endothelial glycocalyx damage and cell viability through IQGAP1/PAR1-2/PI3K/Akt pathway, offering a potential to be a therapeutic target for CVD prevention.

The hemostatic system in chronic brain diseases: A new challenging frontier?

Neurological diseases (ND), including neurodegenerative diseases (NDD) and psychiatric disorders (PD), present a significant public health challenge, ranking third in Europe for disability and premature death, following cardiovascular diseases and cancers. In 2017, approximately 540 million cases of ND were reported among Europe's 925 million people, with strokes, dementia, and headaches being most prevalent. Nowadays, more and more evidence highlight the hemostasis critical role in cerebral homeostasis and vascular events. Indeed, hemostasis, thrombosis, and brain abnormalities contributing to ND form a complex and poorly understood equilibrium. Alterations in vascular biology, particularly involving the blood-brain barrier, are implicated in ND, especially dementia, and PD. While the roles of key coagulation players such as thrombin and fibrinogen are established, the roles of other hemostasis components are less clear. Moreover, the involvement of these elements in psychiatric disease pathogenesis is virtually unstudied, except in specific pathological models such as antiphospholipid syndrome. Advanced imaging techniques, primarily functional magnetic resonance imaging and its derivatives like diffusion tensor imaging, have been developed to study brain areas affected by ND and to improve our understanding of the pathophysiology of these diseases. This literature review aims to clarify the current understanding of the connections between hemostasis, thrombosis, and neurological diseases, as well as explore potential future diagnostic and therapeutic strategies.

Integrated transcriptomics of human blood vessels defines a spatially controlled niche for early mesenchymal progenitor cells

Human blood vessel walls show concentric layers, with the outermost tunica adventitia harboring mesenchymal progenitor cells. These progenitor cells maintain vessel homeostasis and provide a robust cell source for cell-based therapies. However, human adventitial stem cell niche has not been studied in detail. Here, using spatial and single-cell transcriptomics, we characterized the phenotype, potential, and microanatomic distribution of human perivascular progenitors. Initially, spatial transcriptomics identified heterogeneity between perivascular layers of arteries and veins and delineated the tunica adventitia into inner and outer layers. From this spatial atlas, we inferred a hierarchy of mesenchymal progenitors dictated by a more primitive cell with a high surface expression of CD201 (PROCR). When isolated from humans and mice, CD201Low expression typified a mesodermal committed subset with higher osteogenesis and less proliferation than CD201High cells, with a downstream effect on canonical Wnt signaling through DACT2. CD201Low cells also displayed high translational potential for bone tissue generation.

Mice with Reduced PAR4 Reactivity show Decreased Venous Thrombosis and Platelet Procoagulant Activity

Background

Hypercoagulation and thrombin generation are major risk factors for venous thrombosis. Sustained thrombin signaling through PAR4 promotes platelet activation, phosphatidylserine exposure, and subsequent thrombin generation. A single-nucleotide polymorphism in PAR4 (rs2227376) changes proline to leucine extracellular loop 3 (P310L), which decreases PAR4 reactivity and is associated with a lower risk for venous thromboembolism (VTE) in a GWAS meta-analysis.

Objective

The goal of this study is to determine the mechanism for the association of rs2227376 with reduced risk for VTE in using mice with a homologous mutation (PAR4-P322L).

Methods

Venous thrombosis was examined using our recently generated PAR4-P322L mice in the inferior vena cava stasis and stenosis models. Coagulation and clot stability was measured using rotational thromboelastometry (ROTEM). Thrombin generating potential was measured in platelet-rich plasma. Phosphatidylserine surface expression and platelet-neutrophil aggregates were analyzed using flow cytometry.

Results

PAR4P/L and PAR4L/L had reduced incidence and size of venous clots at 48 hours. PAR4P/L and PAR4L/L platelets had progressively decreased phosphatidylserine in response to thrombin and convulxin, which led to decreased thrombin generation and decreased PAR4-mediated platelet-neutrophil aggregation.

Conclusions

The leucine allele in extracellular loop 3, PAR4-322L leads to fewer procoagulant platelets and decreased endogenous thrombin potential. This decreased ability to generate thrombin offers a mechanism for PAR4's role in VTE highlighting a key role for PAR4 signaling.

Coagulation factor X promotes resistance to androgen-deprivation therapy in prostate cancer

Although hypercoagulability is commonly associated with malignancies, whether coagulation factors directly affect tumor cell proliferation remains unclear. Herein, by performing single-cell RNA sequencing (scRNA-seq) of the prostate tumor microenvironment (TME) of mouse models of castration-resistant prostate cancer (CRPC), we report that immunosuppressive neutrophils (PMN-MDSCs) are a key extra-hepatic source of coagulation factor X (FX). FX activation within the TME enhances androgen-independent tumor growth by activating the protease-activated receptor 2 (PAR2) and the phosphorylation of ERK1/2 in tumor cells. Genetic and pharmacological inhibition of factor Xa (FXa) antagonizes the oncogenic activity of PMN-MDSCs, reduces tumor progression, and synergizes with enzalutamide therapy. Intriguingly, F10high PMN-MDSCs express the surface marker CD84 and CD84 ligation enhances F10 expression. Elevated levels of FX, CD84, and PAR2 in prostate tumors associate with worse survival in CRPC patients. This study provides evidence that FXa directly promotes cancer and highlights additional targets for PMN-MDSCs for cancer therapies.

In vivo thrombin activity in the diatom Phaeodactylum tricornutum: biotechnological insights

Diatoms are responsible for 20% of global carbon dioxide fixation and have significant potential in various biotechnological and industrial applications. Recently, the pennate diatom Phaeodactylum tricornutum has emerged as a prominent platform organism for metabolic engineering and synthetic biology. The availability of its genome sequence has facilitated the development of new bioengineering tools. In this study, we used in silico analyses to identify sequences potentially encoding thrombin-like proteins, which are involved in recognizing and cleaving the thrombin sequence LVPRGS in P. tricornutum. Protein structure prediction and docking studies indicated a similar active site and ligand positioning compared to characterized human and bovine thrombin. The evidence and efficiency of the cleavage were determined in vivo using two fusion-protein constructs that included YFP to measure expression, protein accumulation, and cleavage. Western blot analysis revealed 50-100% cleavage between YFP and N-terminal fusion proteins. Our findings suggest the existence of a novel thrombin-like protease in P. tricornutum. This study advances the application of diatoms for the synthesis and production of complex proteins and enhances our understanding of the functional role of these putative thrombin sequences in diatom physiology. KEY POINTS: • Protein structure predictions reveal thrombin-like active sites in P. tricornutum. • Validated cleavage efficiency of thrombin-like protease on fusion proteins in vivo. • Study advances bioengineering tools for diatom-based biotechnological applications.

Steps Toward Recapitulating Endothelium: A Perspective on the Next Generation of Hemocompatible Coatings

Endothelium, the lining in this blood vessel, orchestrates three main critical functions such as protecting blood components, modulating of hemostasis by secreting various inhibitors, and directing clot digestion (fibrinolysis) by activating tissue plasminogen activator. No other surface can perform these tasks; thus, the contact of blood and blood-contacting medical devices inevitably leads to the activation of coagulation, often causing device failure, and thromboembolic complications. This perspective, first, discusses the biological mechanisms of activation of coagulation and highlights the efforts of advanced coatings to recapitulate one characteristic of endothelium, hereafter single functions of endothelium and noting necessity of the synergistic integration of its three main functions. Subsequently, it is emphasized that to overcome the challenges of blood compatibility an endothelium-mimicking system is needed, proposing a synergy of bottom-up synthetic biology, particularly synthetic cells, with passive- and bioactive surface coatings. Such integration holds promise for developing advanced biomaterials capable of recapitulating endothelial functions, thereby enhancing the hemocompatibility and performance of blood-contacting medical devices.

Structural basis of tethered agonism and G protein coupling of protease-activated receptors

Protease-activated receptors (PARs) are a unique group within the G protein-coupled receptor superfamily, orchestrating cellular responses to extracellular proteases via enzymatic cleavage, which triggers intracellular signaling pathways. Protease-activated receptor 1 (PAR1) is a key member of this family and is recognized as a critical pharmacological target for managing thrombotic disorders. In this study, we present cryo-electron microscopy structures of PAR1 in its activated state, induced by its natural tethered agonist (TA), in complex with two distinct downstream proteins, the Gq and Gi heterotrimers, respectively. The TA peptide is positioned within a surface pocket, prompting PAR1 activation through notable conformational shifts. Contrary to the typical receptor activation that involves the outward movement of transmembrane helix 6 (TM6), PAR1 activation is characterized by the simultaneous downward shift of TM6 and TM7, coupled with the rotation of a group of aromatic residues. This results in the displacement of an intracellular anion, creating space for downstream G protein binding. Our findings delineate the TA recognition pattern and highlight a distinct role of the second extracellular loop in forming β-sheets with TA within the PAR family, a feature not observed in other TA-activated receptors. Moreover, the nuanced differences in the interactions between intracellular loops 2/3 and the Gα subunit of different G proteins are crucial for determining the specificity of G protein coupling. These insights contribute to our understanding of the ligand binding and activation mechanisms of PARs, illuminating the basis for PAR1's versatility in G protein coupling.

Current status and perspective on molecular targets and therapeutic intervention strategy in hepatic ischemia-reperfusion injury

Hepatic ischemia‒reperfusion injury (HIRI) is a common and inevitable complication of hepatic trauma, liver resection, or liver transplantation. It contributes to postoperative organ failure or tissue rejection, eventually affecting patient prognosis and overall survival. The pathological mechanism of HIRI is highly complex and has not yet been fully elucidated. The proposed underlying mechanisms include mitochondrial damage, oxidative stress imbalance, abnormal cell death, immune cell hyperactivation, intracellular inflammatory disorders and other complex events. In addition to serious clinical limitations, available antagonistic drugs and specific treatment regimens are still lacking. Therefore, there is an urgent need to not only clarify the exact etiology of HIRI but also reveal the possible reactions and bottlenecks of existing drugs, helping to reduce morbidity and shorten hospitalizations. We analyzed the possible underlying mechanism of HIRI, discussed various outcomes among different animal models and explored neglected potential therapeutic strategies for HIRI treatment. By thoroughly reviewing and analyzing the literature on HIRI, we gained a comprehensive understanding of the current research status in related fields and identified valuable references for future clinical and scientific investigations.

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.

The hypothalamic transcriptome reveals the importance of visual perception on the egg production of Wanxi white geese

Egg performance significantly impacts the development of the local goose industry. The hypothalamus plays an essential role in the egg production of birds. However, few potential candidate genes and biological functions related to egg production in geese have been identified in hypothalamus tissue. In this study, 115 geese were raised and observed for 5 months during the laying period. To understand the regulation mechanism of egg production, the hypothalamus transcriptome profiles of these geese were sequenced using RNA-seq. The hypothalamus samples of four high egg production (HEP) and four low egg production (LEP) geese were selected and collected, respectively. A total of 14,679 genes were identified in the samples. After multiple bioinformatics analyses, Gene Ontology (GO) annotations indicated that genes related to egg production were mainly enriched in biological processes of "response to light stimulus," "sensory system development," and "visual perception." Six potential candidate genes (PDE6C, RHO, MFRP, F2, APOB, and IL6) based on their corresponding GO terms and interaction networks were identified. These identified candidate genes can be used as selection markers to improve the egg production of Wanxi white geese. Our study highlights how visual perception may affect the regulation of geese egg production.

PAR1-mediated Non-periodical Synchronized Calcium Oscillations in Human Mesangial Cells

Mesangial cells offer structural support to the glomerular tuft and regulate glomerular capillary flow through their contractile capabilities. These cells undergo phenotypic changes, such as proliferation and mesangial expansion, resulting in abnormal glomerular tuft formation and reduced capillary loops. Such adaptation to the changing environment is commonly associated with various glomerular diseases, including diabetic nephropathy and glomerulonephritis. Thrombin-induced mesangial remodeling was found in diabetic patients, and expression of the corresponding protease-activated receptors (PARs) in the renal mesangium was reported. However, the functional PAR-mediated signaling in mesangial cells was not examined. This study investigated protease-activated mechanisms regulating mesangial cell calcium waves that may play an essential role in the mesangial proliferation or constriction of the arteriolar cells. Our results indicate that coagulation proteases such as thrombin induce synchronized oscillations in cytoplasmic Ca2+ concentration of mesangial cells. The oscillations required PAR1 G-protein coupled receptors-related activation, but not a PAR4, and were further mediated presumably through store-operated calcium entry and transient receptor potential canonical 3 (TRPC3) channel activity. Understanding thrombin signaling pathways and their relation to mesangial cells, contractile or synthetic (proliferative) phenotype may play a role in the development of chronic kidney disease and requires further investigation.

Discovery of Protease-activated receptor 2 antagonists derived from phenylalanine for the treatment of breast cancer

Protease-activated receptor 2 (PAR2) has garnered attention as a potential therapeutic target in breast cancer. PAR2 is implicated in the activation of extracellular signal-regulated kinase 1/2 (ERK 1/2) via G protein and beta-arrestin pathways, contributing to the proliferation and metastasis of breast cancer cells. Despite the recognized role of PAR2 in breast cancer progression, clinically effective PAR2 antagonists remain elusive. To address this unmet clinical need, we synthesized and evaluated a series of novel compounds that target the orthosteric site of PAR2. Using in silico docking simulations, we identified compound 9a, an optimized derivative of compound 1a ((S)-N-(1-(benzylamino)-1-oxo-3-phenylpropan-2-yl)benzamide), which exhibited enhanced PAR2 antagonistic activity. Subsequent molecular dynamics simulations comparing 9a with the partial agonist 9d revealed that variations in ligand-induced conformational changes and interactions dictated whether the compound acted as an antagonist or agonist of PAR2. The results of this study suggest that further development of 9a could contribute to the advancement of PAR2 antagonists as potential therapeutic agents for breast cancer.

Nanoarchitectonic Engineering of Thermal-Responsive Magnetic Nanorobot Collectives for Intracranial Aneurysm Therapy

Stent-assisted coiling is a main treatment modality for intracranial aneurysms (IAs) in clinics, but critical challenges remain to be overcome, such as exogenous implant-induced stenosis and reliance on antiplatelet agents. Herein, an endovascular approach is reported for IA therapy without stent grafting or microcatheter shaping, enabled by active delivery of thrombin (Th) to target aneurysms using innovative phase-change material (PCM)-coated magnetite-thrombin (Fe3O4-Th@PCM) FTP nanorobots. The nanorobots are controlled by an integrated actuation system of dynamic torque-force hybrid magnetic fields. With robust intravascular navigation guided by real-time ultrasound imaging, nanorobotic collectives can effectively accumulate and retain in model aneurysms constructed in vivo, followed by controlled release of the encapsulated Th for rapid occlusion of the aneurysm upon melting the protective PCM (thermally responsive in a tunable manner) through focused magnetic hyperthermia. Complete and stable aneurysm embolization is confirmed by postoperative examination and 2-week postembolization follow-up using digital subtraction angiography (DSA), contrast-enhanced ultrasound (CEUS), and histological analysis. The safety of the embolization therapy is assessed through biocompatibility evaluation and histopathology assays. This strategy, seamlessly integrating secure drug packaging, agile magnetic actuation, and clinical interventional imaging, avoids possible exogenous implant rejection, circumvents cumbersome microcatheter shaping, and offers a promising option for IA therapy.

Attenuation of Atherosclerosis with PAR4 Deficiency: Differential Platelet Outcomes in apoE -/- vs. Ldlr -/- Mice

Objective

Cardiovascular disease (CVD) is a significant burden globally and, despite current therapeutics, remains the leading cause of death. Platelet inhibitors are of interest in CVD treatment to reduce thrombus formation post-plaque rupture as well their contribution to inflammation throughout the progression of atherosclerosis. Protease activated receptor 4 (PAR4) is a receptor highly expressed by platelets, strongly activated by thrombin, and plays a vital role in platelet activation and aggregation. However, the role of PAR4.

Approach and Results

Mice on a low-density lipoprotein receptor-deficient ( Ldlr -/- ) background were bred with Par4 deficient ( Par4 -/- ) mice to create Ldlr -/- /Par4 +/+ and Ldlr -/- /Par4 -/- cousin lines. Mice were fed high fat (42%) and cholesterol (0.2%) 'Western' diet for 12 weeks for all studies. Bone marrow transplant (BMT) studies were conducted by irradiating Ldlr -/- /Par4 +/+ and Ldlr -/- /Par4 -/- mice with 550 rads (2x, 4 hours apart) and then repopulated with Par4 +/+ or Par4 -/- bone marrow. To determine if the effects of thrombin were mediated solely by PAR4, the thrombin inhibitor dabigatran was added to the 'Western' diet. Ldlr -/- /Par4 -/- given dabigatran did not further decrease their atherosclerotic burden. Differences between apolipoprotein E deficient ( apoE -/- ) and Ldlr -/- platelets were assessed for changes in reactivity. We observed higher PAR4 abundance in arteries with atherosclerosis in human and mice versus healthy controls. PAR4 deficiency attenuated atherosclerosis in the aortic sinus and root versus proficient controls. BMT studies demonstrated this effect was due to hematopoietic cells, most likely platelets. PAR4 appeared to be acting independent of PAR1, as there werer no changes with addition of dabigatran to PAR4 deficient mice. apoE -/- platelets are hyperreactive compared to Ldlr -/- platelets.

Conclusions

Hematopoietic-derived PAR4, most likely platelets, plays a vital role in the development and progression of atherosclerosis. Specific targeting of PAR4 may be a potential therapeutic target for CVD.

Highlights

Deficiency of protease-activated receptor 4 attenuates the development of diet-induced atherosclerosis in a Ldlr -/- mouse model. PAR4 deficiency in hematopoietic cells is atheroprotective. PAR4 deficiency accounts for the majority of thrombin-induced atherosclerosis in a Ldlr -/- mouse model. The examination of platelet-specific proteins and platelet activation should be carefully considered before using the apoE -/- or Ldlr -/- mouse models of atherosclerosis.

Cavβ3 Contributes to the Maintenance of the Blood-Brain Barrier and Alleviates Symptoms of Experimental Autoimmune Encephalomyelitis

BACKGROUND

Tight control of cytoplasmic Ca2+ concentration in endothelial cells is essential for the regulation of endothelial barrier function. Here, we investigated the role of Cavβ3, a subunit of voltage-gated Ca2+ (Cav) channels, in modulating Ca2+ signaling in brain microvascular endothelial cells (BMECs) and how this contributes to the integrity of the blood-brain barrier.

METHODS

We investigated the function of Cavβ3 in BMECs by Ca2+ imaging and Western blot, examined the endothelial barrier function in vitro and the integrity of the blood-brain barrier in vivo, and evaluated disease course after induction of experimental autoimmune encephalomyelitis in mice using Cavβ3-/- (Cavβ3-deficient) mice as controls.

RESULTS

We identified Cavβ3 protein in BMECs, but electrophysiological recordings did not reveal significant Cav channel activity. In vivo, blood-brain barrier integrity was reduced in the absence of Cavβ3. After induction of experimental autoimmune encephalomyelitis, Cavβ3-/- mice showed earlier disease onset with exacerbated clinical disability and increased T-cell infiltration. In vitro, the transendothelial resistance of Cavβ3-/- BMEC monolayers was lower than that of wild-type BMEC monolayers, and the organization of the junctional protein ZO-1 (zona occludens-1) was impaired. Thrombin stimulates inositol 1,4,5-trisphosphate-dependent Ca2+ release, which facilitates cell contraction and enhances endothelial barrier permeability via Ca2+-dependent phosphorylation of MLC (myosin light chain). These effects were more pronounced in Cavβ3-/- than in wild-type BMECs, whereas the differences were abolished in the presence of the MLCK (MLC kinase) inhibitor ML-7. Expression of Cacnb3 cDNA in Cavβ3-/- BMECs restored the wild-type phenotype. Coimmunoprecipitation and mass spectrometry demonstrated the association of Cavβ3 with inositol 1,4,5-trisphosphate receptor proteins.

CONCLUSIONS

Independent of its function as a subunit of Cav channels, Cavβ3 interacts with the inositol 1,4,5-trisphosphate receptor and is involved in the tight control of cytoplasmic Ca2+ concentration and Ca2+-dependent MLC phosphorylation in BMECs, and this role of Cavβ3 in BMECs contributes to blood-brain barrier integrity and attenuates the severity of experimental autoimmune encephalomyelitis disease.

Warfarin-related nephropathy: unveiling the hidden dangers of anticoagulation

Warfarin-related nephropathy (WRN) is defined as acute kidney injury subsequent to excessive anticoagulation with warfarin. Patients with mechanical prosthetic valves require long-term anticoagulant therapy. Nonetheless, warfarin remains the sole available option for anticoagulant therapy. Consequently, patients with mechanical prosthetic valves constitute a special group among the entire anticoagulant population. The present study recorded two cases of patients who had undergone mechanical prosthetic valve surgery and were receiving warfarin therapy. They presented to the hospital with gross hematuria and progressive creatinine levels. Notably, their international normalized ratio (INR) did not exceed three. Subsequent renal biopsies confirmed WRN with IgA nephropathy. The two patients continued to receive warfarin as anticoagulation therapy and were prescribed oral corticosteroids and cyclophosphamide, which resulted in improved renal function during the follow-up. Based on a review of all relevant literature and the present study, we proposed a new challenge: must elevated INR levels be one of the criteria for clinical diagnosis of WRN? Perhaps some inspiration can be drawn from the present article.

Bait and Cleave: Exosite-Binding Peptides on Quantum Dots Selectively Accelerate Protease Activity for Sensing with Enhanced Sensitivity

The advantageous optical properties of quantum dots (QDs) motivate their use in a wide variety of applications related to imaging and bioanalysis, including the detection of proteases and their activity. Recent studies have shown that surface chemistry on QDs is able to modulate protease activity, but only nonspecifically. Here, we present a strategy to selectively accelerate the activity of a particular target protease by as much as two orders of magnitude. Exosite-binding "bait" peptides were derived from proteins that span a range of biological roles─substrate, receptor, and inhibitor─and were used to increase the affinity of the QD-peptide conjugates for either thrombin or factor Xa, resulting in increased rates of proteolysis for coconjugated substrates. Unlike effects from QD surface chemistry, the acceleration was specific to the target protease with negligible acceleration of other proteases. Benefits of this "bait and cleave" sensing approach included detection limits that improved by more than an order of magnitude, reenabled detection of target protease against an overwhelming background of nontarget proteolysis, and mitigation of the action of inhibitors. The cumulative results point to a generalizable strategy, where the mechanism of acceleration, considerations for the design of bait peptides and conjugates, and routes to expanding the scope of this approach are discussed. Overall, this research represents a major step forward in the rational design of nanoparticle-based enzyme sensors that enhance sensitivity and selectivity.

Scaffold-Mediated Drug Delivery for Enhanced Wound Healing: A Review

Wound healing is a complex physiological process involving coordinated cellular and molecular events aimed at restoring tissue integrity. Acute wounds typically progress through the sequential phases of hemostasis, inflammation, proliferation, and remodeling, while chronic wounds, such as venous leg ulcers and diabetic foot ulcers, often exhibit prolonged inflammation and impaired healing. Traditional wound dressings, while widely used, have limitations such poor moisture retention and biocompatibility. To address these challenges and improve patient outcomes, scaffold-mediated delivery systems have emerged as innovative approaches. They offer advantages in creating a conducive environment for wound healing by facilitating controlled and localized drug delivery. The manuscript explores scaffold-mediated delivery systems for wound healing applications, detailing the use of natural and synthetic polymers in scaffold fabrication. Additionally, various fabrication techniques are discussed for their potential in creating scaffolds with controlled drug release kinetics. Through a synthesis of experimental findings and current literature, this manuscript elucidates the promising potential of scaffold-mediated drug delivery in improving therapeutic outcomes and advancing wound care practices.

Hemin/G-quadruplex and AuNPs-MoS2 based novel dual signal amplification strategy for ultrasensitively sandwich-type electrochemical thrombin aptasensor

In this work, a novel sandwich-type electrochemical aptasensor based on the dual signal amplification strategy of hemin/G-quadruplex and AuNPs-MoS2 was designed and constructed, which realized the highly sensitive and specific detection of thrombin (TB). In this aptasensor, the 15-mer TB-binding aptamer (TBA-1) modified with thiol group was immobilized on the surface of AuNPs modified glassy carbon electrode (AuNPs/GCE) as capturing elements. Another thiol-modified 29-mer TB-binding aptamer (TBA-2) sequence containing G-quadruplex structure for hemin immobilization was designed. The formed hemin/G-quadruplex/TBA-2 sequence was further combined to the AuNPs decorated flower-like molybdenum disulfide (AuNPs-MoS2) composite surface via Au-S bonds, acting the role of reporter probe. In presence of the target TB, the sandwich-type electrochemical aptamer detection system could be formed properly. With the assistance of the dual signal amplification of AuNPs-MoS2 and hemin/G-quadruplex toward H2O2 reduction, the sandwich-type electrochemical aptasensor was successfully constructed for sensitive detection of TB. The results demonstrate that the fabricated aptasensor displays a wide linear range of 1.0 × 10-6 ∼ 10.0 nM with a low detection limit of 0.34 fM. This proposed aptasensor shows potential application in the detection of TB content in real biological samples with high sensitivity, selectivity, and reliability.

Topical lyophilized thrombin application improves wound healing for posterior spinal surgery

Background

The erector spinae plane block (ESPB) was proposed as a part of the postoperative multimodal analgesic regimen to improve pain management after posterior spinal surgery. However, ESPB might cause more surgical incisional wound exudate and poor wound healing, which might be improved after topical lyophilized thrombin application.

Materials and methods

We performed a retrospective study on patients who received posterior spinal surgery between January 2018 and December 2021. These patients were assigned into three groups: group A (general anesthesia), group B (general anesthesia with ESPB), and group C (general anesthesia with ESPB and topical 1000-unit thrombin application). Postoperative outcomes, including times of dressing changes, duration of suture removal, and incisional wound healing, were compared among these groups.

Results

Our study included 89 patients, with 48, 20, and 21 patients in groups A, B, and C, respectively. Baseline demographics, height, weight, comorbidities, and operation duration were comparable among the three groups. Group B required statistically significantly more dressing changes and had a prolonged duration of suture removal than group A (9.4 ± 4.7 versus 6.5 ± 2.0 times, 16.2 ± 3.7 versus 14.2 ± 1.4 days, respectively), which could be statistically significantly improved after the thrombin application in group C. Group B also had more frequent poor wound healing (25.0 %), which could also be improved after the thrombin application (0.0 %).

Conclusions

ESPB could cause more dressing changes and poor surgical wound healing after posterior spinal surgery, which could be improved by topical lyophilized thrombin powder application.

Sono-responsive smart nanoliposomes for precise and rapid hemostasis application

Massive hemorrhage caused by injuries and surgical procedures is a major challenge in emergency medical scenarios. Conventional means of hemostasis often fail to rapidly and efficiently control bleeding, especially in inaccessible locations. Herein, a type of smart nanoliposome with ultrasonic responsiveness, loaded with thrombin (thrombin@liposome, named TNL) was developed to serve as an efficient and rapid hemostatic agent. Firstly, the hydrophilic cavities of the liposomes were loaded onto the sono-sensitive agent protoporphyrin. Secondly, a singlet oxygen-sensitive chemical bond was connected with the hydrophobic and hydrophilic ends of liposomes in a chemical bond manner. Finally, based on the host guest effect between ultrasound and the sono-sensitizer, singlet oxygen is continuously generated, which breaks the hydrophobic and hydrophilic ends of liposome fragments, causing spatial collapse of the TNL structure, swiftly releases thrombin loaded in the hydrophilic capsule cavity, thereby achieving accurate and rapid local hemostasis (resulted in a reduction of approximately 67% in bleeding in the rat hemorrhage model). More importantly, after thorough assessments of biocompatibility and biodegradability, it has been confirmed that TNL possesses excellent biosafety, providing a new avenue for efficient and precise hemostasis.

An electrochemical biosensor for the amplification of thrombin activity by perylene-mediated photoinitiated polymerization

BACKGROUND

Thrombin, a coagulation system protease, is a key enzyme involved in the coagulation cascade and has been developed as a marker for coagulation disorders. However, the methods developed in recent years have the disadvantages of complex operation, long reaction time, low specificity and sensitivity. Meanwhile, thrombin is at a lower level in the pre-disease period. Therefore, to accurately diagnose the disease, it is necessary to develop a fast, simple, highly sensitive and specific method using signal amplification technology.

RESULTS

We designed an electrochemical biosensor based on photocatalytic atom transfer radical polymerization (photo-ATRP) signal amplification for the detection of thrombin. Sulfhydryl substrate peptides (without carboxyl groups) are self-assembled to the gold electrode surface via Au-S bond and serve as thrombin recognition probes. The substrate peptide is cleaved in the presence of thrombin to generate -COOH, which can form a carboxylate-Zr(IV)-carboxylate complex via Zr(IV) and initiator (α-bromophenylacetic acid, BPAA). Subsequently, an electrochemical biosensor was prepared by introducing polymer chains with electrochemical signaling molecules (ferrocene, Fc) onto the electrode surface by photocatalytic (perylene, Py) mediated ATRP using ferrocenylmethyl methacrylate (FMMA) as a monomer. The concentration of thrombin was evaluated by the voltammetric signal generated by square wave voltammetry (SWV), and the result showed that the biosensor was linear between 1.0 ng/mL ∼ 10 fg/mL, with a lower detection limit of 4.0 fg/mL (∼0.1 fM). Moreover, it was shown to be highly selective for thrombin activity in complex serum samples and for thrombin inhibition screening.

SIGNIFICANCE

The biosensor is an environmentally friendly and economically efficient strategy while maintaining the advantages of high sensitivity, anti-interference, good stability and simplicity of operation, which has great potential for application in the analysis of complex samples.

Salvianolic acid B inhibits thrombosis and directly blocks the thrombin catalytic site

Background

Salvianolic acid B (SAB) is a major component of Salvia miltiorrhiza root (Danshen), widely used in East/Southeast Asia for centuries to treat cardiovascular diseases. Danshen depside salt, 85% of which is made up of SAB, is approved in China to treat chronic angina. Although clinical observations suggest that Danshen extracts inhibited arterial and venous thrombosis, the exact mechanism has not been adequately elucidated.

Objective

To delineate the antithrombotic mechanisms of SAB.

Methods

We applied platelet aggregation and coagulation assays, perfusion chambers, and intravital microscopy models. The inhibition kinetics and binding affinity of SAB to thrombin are measured by thrombin enzymatic assays, intrinsic fluorescence spectrophotometry, and isothermal titration calorimetry. We used molecular in silico docking models to predict the interactions of SAB with thrombin.

Results

SAB dose-dependently inhibited platelet activation and aggregation induced by thrombin. SAB also reduced platelet aggregation induced by adenosine diphosphate and collagen. SAB attenuated blood coagulation by modifying fibrin network structures and significantly decreased thrombus formation in mouse cremaster arterioles and perfusion chambers. The direct SAB-thrombin interaction was confirmed by enzymatic assays, intrinsic fluorescence spectrophotometry, and isothermal titration calorimetry. Interestingly, SAB shares key structural similarities with the trisubstituted benzimidazole class of thrombin inhibitors, such as dabigatran. Molecular docking models predicted the binding of SAB to the thrombin active site.

Conclusion

Our data established SAB as the first herb-derived direct thrombin catalytic site inhibitor, suppressing thrombosis through both thrombin-dependent and thrombin-independent pathways. Purified SAB may be a cost-effective agent for treating arterial and deep vein thrombosis.

Recombinant hirudin suppresses angiogenesis of diffuse large B-cell lymphoma through regulation of the PAR-1-VEGF

Hirudin is one of the specific inhibitors of thrombin, which has been confirmed to have strong bioactivities, including inhibiting tumors. However, the function and mechanism of hirudin and protease-activated receptor 1 (PAR-1) in diffuse large B-cell lymphoma (DLBCL) have not been clear. Detecting the expression PAR-1 in DLBCL tissues and cells by RT-qPCR and IHC. Transfected sh-NC, sh-PAR-1, or pcDNA3.1-PAR-1 in DLBCL cells or processed DLBCL cells through added thrombin, Vorapaxar, Recombinant hirudin (RH), or Na2S2O4 and co-culture with EA.hy926. And built DLBCL mice observed tumor growth. Detecting the expression of related genes by RT-qPCR, Western blot, IHC, and immunofluorescence, measured the cellular hypoxia with Hypoxyprobe-1 Kit, and estimated the cell inflammatory factors, proliferation, migration, invasion, and apoptosis by ELISA, CCK-8, flow cytometry, wound-healing and Transwell. Co-immunoprecipitation and pull-down measurement were used to verify the relationship. PAR-1 was highly expressed in DLBCL tissues and cells, especially in SUDHL2. Na2S2O4 induced SUDHL2 hypoxia, and PAR-1 did not influence thrombin-activated hypoxia. PAR-1 could promote SUDHL2 proliferation, migration, and invasion, and it was unrelated to cellular hypoxia. PAR-1 promoted proliferation, migration, and angiogenesis of EA.hy926 or SUDHL2 through up-regulation vascular endothelial growth factor (VEGF). RH inhibited tumor growth, cell proliferation, and migration, promoted apoptosis of DLBCL, and inhibited angiogenesis by down-regulating PAR-1-VEGF. RH inhibits proliferation, migration, and angiogenesis of DLBCL cells by down-regulating PAR-1-VEGF.

Coagulation Protease-Driven Cancer Immune Evasion: Potential Targets for Cancer Immunotherapy

Blood coagulation and cancer are intrinsically connected, hypercoagulation-associated thrombotic complications are commonly observed in certain types of cancer, often leading to decreased survival in cancer patients. Apart from the common role in coagulation, coagulation proteases often trigger intracellular signaling in various cancers via the activation of a G protein-coupled receptor superfamily protease: protease-activated receptors (PARs). Although the role of PARs is well-established in the development and progression of certain types of cancer, their impact on cancer immune response is only just emerging. The present review highlights how coagulation protease-driven PAR signaling plays a key role in modulating innate and adaptive immune responses. This is followed by a detailed discussion on the contribution of coagulation protease-induced signaling in cancer immune evasion, thereby supporting the growth and development of certain tumors. A special section of the review demonstrates the role of coagulation proteases, thrombin, factor VIIa, and factor Xa in cancer immune evasion. Targeting coagulation protease-induced signaling might be a potential therapeutic strategy to boost the immune surveillance mechanism of a host fighting against cancer, thereby augmenting the clinical consequences of targeted immunotherapeutic regimens.

The Complex Role of Thrombin in Cancer and Metastasis: Focus on Interactions with the Immune System

Thrombin, a pleiotropic enzyme involved in coagulation, plays a crucial role in both procoagulant and anticoagulant pathways. Thrombin converts fibrinogen into fibrin, initiates platelet activation, and promotes clot formation. Thrombin also activates anticoagulant pathways, indirectly inhibiting factors involved in coagulation. Tissue factor triggers thrombin generation, and the overexpression of thrombin in various cancers suggests that it is involved in tumor growth, angiogenesis, and metastasis. Increased thrombin generation has been observed in cancer patients, especially those with metastases. Thrombin exerts its effects through protease-activated receptors (PARs), particularly PAR-1 and PAR-2, which are involved in cancer progression, angiogenesis, and immunological responses. Thrombin-mediated signaling promotes angiogenesis by activating endothelial cells and platelets, thereby releasing proangiogenic factors. These functions of thrombin are well recognized and have been widely described. However, in recent years, intriguing new findings concerning the association between thrombin activity and cancer development have come to light, which justifies a review of this research. In particular, there is evidence that thrombin-mediated events interact with the immune system, and may regulate its response to tumor growth. It is also worth reevaluating the impact of thrombin on thrombocytes in conjunction with its multifaceted influence on tumor progression. Understanding the role of thrombin/PAR-mediated signaling in cancer and immunological responses is crucial, particularly in the context of developing immunotherapies. In this systematic review, we focus on the impact of the thrombin-related immune system response on cancer progression.

Ex Vivo Antiplatelet Effects of Oral Anticoagulants

BACKGROUND

The impact of non-vitamin K antagonist oral anticoagulants (NOACs) on platelet function is still unclear. We conducted a comprehensive ex vivo study aimed at assessing the effect of the four currently marketed NOACs on platelet function.

METHODS

We incubated blood samples from healthy donors with concentrations of NOACs (50, 150 and 250 ng/mL), in the range of those achieved in the plasma of patients during therapy. We evaluated generation of thrombin; light transmittance platelet aggregation (LTA) in response to adenosine diphosphate (ADP), thrombin receptor-activating peptide (TRAP), human γ-thrombin (THR) and tissue factor (TF); generation of thromboxane (TX)B2; and expression of protease-activated receptor (PAR)-1 and P-selectin on the platelet surface.

RESULTS

All NOACs concentration-dependently reduced thrombin generation compared with control. THR-induced LTA was suppressed by the addition of dabigatran at any concentration, while TF-induced LTA was reduced by factor-Xa inhibitors. ADP- and TRAP-induced LTA was not modified by NOACs. TXB2 generation was reduced by all NOACs, particularly at the highest concentrations. We found a concentration-dependent increase in PAR-1 expression after incubation with dabigatran, mainly at the highest concentrations, but not with FXa inhibitors; P-selectin expression was not changed by any drugs.

CONCLUSIONS

Treatment with the NOACs is associated with measurable ex vivo changes in platelet function, arguing for antiplatelet effects beyond the well-known anticoagulant activities of these drugs. There are differences, however, among the NOACs, especially between dabigatran and the FXa inhibitors.

A sodium alginate - silk fibroin biosponge loaded with thrombin: Effective hemostasis and wound healing

In trauma first aid, rapid hemostasis is a priority, extricating patients from hemorrhagic shock and infection risks. This paper explores novel hemostatic materials, using ion-crosslinking and freeze-drying techniques. Iterative experiments determined optimal conditions for the temperature-variable mixing-freeze-drying chemical reaction of sodium alginate (SA)/silk fibroin (SF). We used SA, SA/SF, SA/SF-TB and commercial hemostatic sponge control samples to perform hemostasis experiments on rat liver injury and femoral artery injury models, and to perform wound healing experiments on rat back full-layer skin. The results showed that the hemostatic time and blood loss of SA/SF-TB group rats (liver hemorrhage model: 397.17 ± 34.80 mg, 77.83 ± 7.41 s; Femoral artery bleeding model: 940.33 ± 41.93 mg, 96.83 ± 4.07 s) was significantly better than other experimental groups, and similar to the commercial group. The wound healing experiment showed that the new granulation tissue thickness of SA/SF-TB group was thicker (380.39 ± 28.56 μm) at day 14. In addition, the material properties and biocompatibility of sponges were characterized by cell experiments and in vivo embedding experiments. All the results showed that the SA/SF-TB hemostatic sponge prepared in this study could not only seal the wound quickly and stop bleeding, but also promote the growth of epidermal cells and fibroblasts and accelerate wound healing. This new material solves the shortcomings of traditional materials such as low stability, limited shelf life, high unit price, and has good biocompatibility, easy preparation, rapid hemostasis and other excellent properties. Therefore, this innovative hemostatic material has great prospects and potential in clinical applications.

Discovery of Potent and Selective Quinoxaline-Based Protease-Activated Receptor 4 (PAR4) Antagonists for the Prevention of Arterial Thrombosis

PAR4 is a promising antithrombotic target with potential for separation of efficacy from bleeding risk relative to current antiplatelet therapies. In an effort to discover a novel PAR4 antagonist chemotype, a quinoxaline-based HTS hit 3 with low μM potency was identified. Optimization of the HTS hit through the use of positional SAR scanning and the design of conformationally constrained cores led to the discovery of a quinoxaline-benzothiazole series as potent and selective PAR4 antagonists. The lead compound 48, possessing a 2 nM IC50 against PAR4 activation by γ-thrombin in platelet-rich plasma (PRP) and greater than 2500-fold selectivity versus PAR1, demonstrated robust antithrombotic efficacy and minimal bleeding in the cynomolgus monkey models.

Thrombin and Thrombin-Incorporated Biomaterials for Disease Treatments

Thrombin, a coagulation-inducing protease, has long been used in the hemostatic field. During the past decades, many other therapeutic uses of thrombin have been developed. For instance, burn treatment, pseudoaneurysm therapy, wound management, and tumor vascular infarction (or tumor vasculature blockade therapy) can all utilize the unique and powerful function of thrombin. Based on their therapeutic effects, many thrombin-associated products have been certificated by the Food and Drug Administration, including bovine thrombin, human thrombin, recombinant thrombin, fibrin glue, etc. Besides, several thrombin-based drugs are currently undergoing clinical trials. In this article, the therapeutic uses of thrombin (from the initial hemostasis to the latest cancer therapy), the commercially available drugs associated with thrombin, and the pros and cons of thrombin-based therapeutics (e.g., adverse immune responses related to bovine thrombin, thromboinflammation, and vasculogenic "rebounds") are summarized. Further, the current challenges and possible future research directions of thrombin-incorporated biomaterials and therapies are discussed. It is hoped that this review may provide a valuable reference for researchers in this field and help them to design safer and more effective thrombin-based drugs for fighting against various intractable diseases.