Platelets and primary haemostasis

Effect of toxins from different periodontitis-associated bacteria on human platelet function

BACKGROUND

Periodontitis is caused by a dysbiosis of oral bacteria resulting in alveolar bone destruction and teeth loss. The role of platelets in pathogenesis of periodontitis is a subject of research. The release of toxins from periodontitis-associated bacteria may influence platelet function and contribute to the modulation of hemostatic or inflammatory responses. Therefore, we explored platelet function upon exposure to defined toxins: leukotoxin A from Aggregatibacter actinomycetemcomitans (LtxA), a synthetic version of the C14-Tri-LAN-Gly peptide from Fusobacterium nucleatum (C14), and lipopolysaccharides from Porphyromonas gingivalis (LPS).

METHODS

Light transmission aggregometry was performed after the addition of toxins to platelet-rich plasma in different doses. Flow cytometry was used to identify inhibitory effects of toxins by measuring phosphorylation of the vaso-dilator-stimulated phosphoprotein or to identify activating effects by the detection of CD62P expression. The release of chemokines derived from washed platelets was determined by immunoassays.

RESULTS

Collagen-induced threshold aggregation values were diminished upon incubation with LtxA and C14, accompanied with an increase of vaso-dilator-stimulated phosphoprotein (VASP) phosphorylation, indicating platelet inhibition. In contrast, LPS did not affect aggregation but slightly enhanced CD62P expression under co-stimulation with low-dose thrombin pointing to slight platelet activation. The three toxins did not relevantly influence the secretion of chemokines.

CONCLUSIONS

Although weak, the investigated toxins differently influenced human platelet function. LtxA and C14 mediated inhibitory effects, whereas LPS contributed to a slight activation of platelets. Further analysis of specific cellular responses mediated by bacterial toxins may render novel targets and suggestions for the treatment of periodontitis.

Use of clinical biological tests of haemostasis to evaluate topical haemostatics

INTRODUCTION

In addition to traditional means, topical haemostatics are currently used to avoid haemorrhage during surgery. Although they have been reported to be effective, there is a low level of proof of their clinical efficacy, which is at odds with their levels of use. This study used two methods to better understand their in vitro mechanism of action.

METHODS

Two clinical biology assays were used to measure the action of topical haemostatics on primary and secondary haemostasis. Calibrated samples of collagen sponges and polypropylene non-woven gauze were tested. Platelet aggregation was assessed using a multichannel aggregometer. A thrombin generation assay (TGA) was used with a fluorogenic readout. Tissue factor solutions were used to activate coagulation.

RESULTS

In terms of primary haemostasis, collagen sponges stimulated platelet aggregation, in particular between 2 and 5 min after incubation with platelet-rich plasma and with no dose effect. In regard to coagulation, the kinetics of thrombin generation was enhanced. Polypropylene non-woven gauze did not exhibit any effect on platelet aggregation, although it did have a weak effect on the kinetics of thrombin generation.

CONCLUSION

Collagen is well known to exert a haemostatic effect due to its action on platelet aggregation. By contrast, polypropylene non-woven gauze has not been shown to have any effect on platelet aggregation other than a minor impact on thrombin generation. The results obtained with the devices tested are in agreement with the literature. Platelet aggregation biological assays and TGA measurements appear to be suitable for evaluation of these medical products.

Roles of G proteins and their GTPase-activating proteins in platelets

Platelets are small anucleate blood cells supporting vascular function. They circulate in a quiescent state monitoring the vasculature for injuries. Platelets adhere to injury sites and can be rapidly activated to secrete granules and to form platelet/platelet aggregates. These responses are controlled by signalling networks that include G proteins and their regulatory guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Recent proteomics studies have revealed the complete spectrum of G proteins, GEFs, and GAPs present in platelets. Some of these proteins are specific for platelets and very few have been characterised in detail. GEFs and GAPs play a major role in setting local levels of active GTP-bound G proteins in response to activating and inhibitory signals encountered by platelets. Thus, GEFs and GAPs are highly regulated themselves and appear to integrate G protein regulation with other cellular processes. This review focuses on GAPs of small G proteins of the Arf, Rab, Ras, and Rho families, as well as of heterotrimeric G proteins found in platelets.

Platelet-derived mitochondria transfer facilitates wound-closure by modulating ROS levels in dermal fibroblasts

Platelets are known to improve the wound-repair capacity of mesenchymal stem cells (MSCs) by transferring mitochondria intercellularly. This study aimed to investigate whether direct transfer of mitochondria (pl-MT) isolated from platelets could enhance wound healing in vitro using a cell-based model. Wound repairs were assessed by 2D gap closure experiment in wound scratch assay using human dermal fibroblasts (hDFs). Results demonstrated that pl-MT were successfully internalized into hDFs. It increased cell proliferation and promoted the closure of wound gap. Importantly, pl-MT suppressed both intracellular and mitochondrial ROS production induced by hydrogen peroxide, cisplatin, and TGF-β in hDFs. Taken together, these results suggest that pl-MT transfer might be used as a potential therapeutic strategy for wound repair.

Influencing factors of anthracycline-induced subclinical cardiotoxicity in acute leukemia patients

BACKGROUND

Current treatment of acute leukemia is based on anthracycline chemotherapy. Anthracyclines, despite improving patient survival, have serious cardiotoxicity and therefore cardiac monitoring should be a priority. The purpose of this study is to explore the possible early predictors of anthracycline-induced subclinical cardiotoxicity(AISC)in acute leukemia patients.

METHODS

We conducted a prospective observational study involving 51 patients with acute leukemia treated with anthracycline. Demographic data, clinical variables, echocardiography variables and biochemical variables were collected at baseline and after 3 cycles of chemotherapy. Patients were divided into the AISC and No-AISC groups according to changes of global longitudinal peak systolic strain. Regression models and receiver operating characteristic curve analysis were used to explore the relationship between the variables and AISC.

RESULT

17 of the patients suffered subclinical cardiotoxicity after 3 cycles of anthracycline treatment. Multiple logistic regression analysis showed a significant association of DBil (OR 0.612, 95% CI 0.409-0.916, p = 0.017), TBil (OR 0.841, 95% CI 0.717-0.986, p = 0.033), PLT (OR 1.012, 95% CI 1.002-1.021, p = 0.016) and Glu (OR 1.873, 95% CI 1.009-3.475, p = 0.047) with the development of AISC. After 3 cycles of chemotherapy, there was a significant difference in PLT between the AISC and NO-AISC groups. Moreover, the dynamic changes in PLT from baseline to after 3 cycles of chemotherapy were each statistically significant in the AISC and NO-AISC groups. The combination of PLT and N-terminal pro-B-type natriuretic peptide (NT-proBNP) had the highest area under curves (AUC) for the diagnosis of AISC than PLT and NT-proBNP alone (AUC = 0.713, 95%CI: 0.56-0.87, P = 0.017).

CONCLUSION

Total bilirubin (TBil), direct bilirubin (DBil), platelets (PLT) and blood glucose (Glu) are independent influencing factors for AISC in acute leukemia patients receiving anthracycline therapy. Bilirubin may be a protective factor and PLT may be a contributing factor for AISC. The combination of baseline PLT and baseline NT-proBNP shows satisfactory predictive ability for AISC in acute leukemia cases treated with 3 cycles of chemotherapy.

Platelet-derived extracellular vesicles for drug delivery

Platelet-derived extracellular vesicles (PEVs) are a subset of EVs that are released from platelets, which are small nuclear cell fragments that play a critical role in hemostasis and thrombosis. PEVs have been shown to have important roles in a variety of physiological and pathological processes, including inflammation, angiogenesis, and cancer. Recently, researchers, including our group have utilized PEVs as drug delivery platforms as PEVs could target inflammatory sites both passively and actively. This review summarizes the biological function of PEVs, introduces recent applications of PEVs in targeted drug delivery, and provides an outlook for the further development of utilizing PEVs for drug delivery.

A case of acquired thrombotic thrombocytopenic purpura induced by acute severe hepatitis E: successfully treated by plasma exchange and rituximab

With its low morbidity and high mortality rates, thrombotic thrombocytopenic purpura (TTP) has imposed a critical physical and economic burden on both society and individuals. Thrombocytopenia commonly occurs in severe liver failure, and a variety of hepatitis viruses are known to induce immune thrombocytopenic purpura. However, TTP is extremely rare in hepatitis E virus infection. We hereby report a case of a 53-year-old male who present with TTP caused by severe hepatitis E, and the patients achieved successful recovery after treatment. Therefore, we propose considering AMAMTS13 testing as an essential and beneficial approach for accurately diagnosing and treating patients with severe hepatitis or infection with notable platelet decline.

Vagus nerve stimulation primes platelets and reduces bleeding in hemophilia A male mice

Deficiency of coagulation factor VIII in hemophilia A disrupts clotting and prolongs bleeding. While the current mainstay of therapy is infusion of factor VIII concentrates, inhibitor antibodies often render these ineffective. Because preclinical evidence shows electrical vagus nerve stimulation accelerates clotting to reduce hemorrhage without precipitating systemic thrombosis, we reasoned it might reduce bleeding in hemophilia A. Using two different male murine hemorrhage and thrombosis models, we show vagus nerve stimulation bypasses the factor VIII deficiency of hemophilia A to decrease bleeding and accelerate clotting. Vagus nerve stimulation targets acetylcholine-producing T lymphocytes in spleen and α7 nicotinic acetylcholine receptors (α7nAChR) on platelets to increase calcium uptake and enhance alpha granule release. Splenectomy or genetic deletion of T cells or α7nAChR abolishes vagal control of platelet activation, thrombus formation, and bleeding in male mice. Vagus nerve stimulation warrants clinical study as a therapy for coagulation disorders and surgical or traumatic bleeding.

Intravenous Hemostats: Foundation, Targeting, and Controlled-Release

Uncontrollable blood loss is the greatest cause of mortality in prehospital patients and the main source of disability and death in hospital care. Compared with external hemostats, intravenous hemostats are more appropriate for preventing and treating uncontrolled bleeding in vivo and large bleeding on the body surface. This Review initially establishes intravenous hemostats' response basis, including the coagulation mechanism, fibrinolytic pathway, and protein corona. Second, the study of advancement of intravenous hemostat targeting was expanded from two perspectives, cellular hemostatic agents and synthetic hemostatic agents. Meanwhile, after discussing the progress of controlled-release intravenous hemostats with platelets as the stimuli, this Review offers insight into the possibility of controlled-release intravenous hemostats with microenvironment as the stimuli, combining the studies of controlled-release targeted thrombolysis.

Targeting Platelet Activation Pathways to Limit Tumour Progression: Current State of Affairs

The association between cancer and a hypercoagulatory environment is well described. Thrombotic complications serve not only as a major mortality risk but the underlying molecular structure and function play significant roles in enhancing tumour progression, which is defined as the tumour's capacity to survive, invade and metastasise, amongst other hallmarks of the disease. The use of anticoagulant or antiplatelet drugs in cardiovascular disease lessens thrombotic effects, but the consequences on tumour progression require interrogation. Therefore, this review considered developments in the management of platelet activation pathways (thromboxane, ADP and thrombin), focusing on the use of Aspirin, Clopidogrel and Atopaxar, and their potential impacts on tumour progression. Published data suggested a cautionary tale in ensuring we adequately investigate not only drug-drug interactions but also those unforeseen reciprocal interactions between drugs and their targets within the tumour microenvironment that may act as selective pressures, enhancing tumour survival and progression.

Regulatory Effects of Curcumin on Platelets: An Update and Future Directions

The rhizomatous plant turmeric, which is frequently used as a spice and coloring ingredient, yields curcumin, a bioactive compound. Curcumin inhibits platelet activation and aggregation and improves platelet count. Platelets dysfunction results in several disorders, including inflammation, atherothrombosis, and thromboembolism. Several studies have proved the beneficial role of curcumin on platelets and hence proved it is an important candidate for the treatment of the aforementioned diseases. Moreover, curcumin is also frequently employed as an anti-inflammatory agent in conventional medicine. In arthritic patients, it has been shown to reduce the generation of pro-inflammatory eicosanoids and to reduce edema, morning stiffness, and other symptoms. Curcumin taken orally also reduced rats' acute inflammation brought on by carrageenan. Curcumin has also been proven to prevent atherosclerosis and platelet aggregation, as well as to reduce angiogenesis in adipose tissue. In the cerebral microcirculation, curcumin significantly lowered platelet and leukocyte adhesion. It largely modulated the endothelium to reduce platelet adhesion. Additionally, P-selectin expression and mice survival after cecal ligation and puncture were improved by curcumin, which also altered platelet and leukocyte adhesion and blood-brain barrier dysfunction. Through regulating many processes involved in platelet aggregation, curcuminoids collectively demonstrated detectable antiplatelet activity. Curcuminoids may therefore be able to prevent disorders linked to platelet activation as possible therapeutic agents. This review article proposes to highlight and discuss the regulatory effects of curcumin on platelets.

Platelet signaling at the nexus of innate immunity and rheumatoid arthritis

Rheumatoid arthritis (RA) is a debilitating autoimmune disorder characterized by chronic inflammation of the synovial tissues and progressive destruction of bone and cartilage. The inflammatory response and subsequent tissue degradation are orchestrated by complex signaling networks between immune cells and their products in the blood, vascular endothelia and the connective tissue cells residing in the joints. Platelets are recognized as immune-competent cells with an important role in chronic inflammatory diseases such as RA. Here we review the specific aspects of platelet function relevant to arthritic disease, including current knowledge of the molecular crosstalk between platelets and other innate immune cells that modulate RA pathogenesis.

Coagulation and complement: Key innate defense participants in a seamless web

In 1969, Dr. Oscar Ratnoff, a pioneer in delineating the mechanisms by which coagulation is activated and complement is regulated, wrote, “In the study of biological processes, the accumulation of information is often accelerated by a narrow point of view. The fastest way to investigate the body’s defenses against injury is to look individually at such isolated questions as how the blood clots or how complement works. We must constantly remind ourselves that such distinctions are man-made. In life, as in the legal cliché, the devices through which the body protects itself form a seamless web, unwrinkled by our artificialities.” Our aim in this review, is to highlight the critical molecular and cellular interactions between coagulation and complement, and how these two major component proteolytic pathways contribute to the seamless web of innate mechanisms that the body uses to protect itself from injury, invading pathogens and foreign surfaces.

Functional analysis and expression profile of human platelets infected by EBV in vitro

Platelet activation is commonly detected after infection by multiple viruses such as human immunodeficiency virus (HIV), H1N1 influenza, Hepatitis C virus (HCV), Ebola virus (EBV), and Dengue virus (DENV). Non-coding RNAs (ncRNAs) constitute the majority of the human transcribed genome, but the biology of platelet ncRNAs is largely unexplored. In this study, we performed microarray profiling to characterize the expression profile of human platelets infected with EBV in vitro after 2 h. A total of 187 long non-coding RNAs (lncRNAs) displayed differences, of which 114 were upregulated and 73 were downregulated; 78 microRNAs (miRNAs) showed differences, including 73 upregulated and 5 downregulated; 808 mRNAs displayed differences, among which 367 were upregulated and 441 were downregulated. Gene ontology (GO) analysis mostly related to G protein-coupled receptor signaling pathway, detection of chemical stimulus involved in sensory perception of smell and regulation of transcription by RNA polymerase II. Pathway analysis showed that the differentially expressed genes were mainly enriched in cell metabolism and immune-related response. A ceRNA network was established based on predicting regulatory pairs in differentially expressed genes, in which hsa-miR-6877-3p had the highest regulatory capability (degree = 31), FAM230A was the lncRNA with the highest regulatory capability (degree = 28). According to the EBV related miRNA regulation network, it revealed that ebv-miR-BART19-3p had the most target genes and BRWD1, FAM126B, TFRC and JMY were the genes most regulated by EBV-related miRNAs. After overlapping the three networks, we found that the EIFAK2 gene was strongly correlated with autologous ncRNAs, including hsa-miR-1972, hsa-miR-504-3p and hsa-miR-6825-5p, as well as with EBV ncRNAs, including EBER1, EBER2, miR-BART7-3p and miR-BART16. The present study contributes to a better understanding of the expression profiling of ncRNAs and their functions in platelets activated by EBV in vitro, and paves the way to further study on platelet function.

Chemokine PF4 Inhibits EV71 and CA16 Infections at the Entry Stage

Platelet factor 4 (PF4) or the CXC chemokine CXCL4 is the most abundant protein within the α-granules of platelets. Previous studies found that PF4 regulates infections of several viruses, including HIV-1, H1N1, hepatitis C virus (HCV), and dengue virus. Here, we show that PF4 is an inhibitor of enterovirus A71 (EV71) and coxsackievirus A16 (CA16) infections. The secreted form of PF4 from transfected cells or soluble purified PF4 from Escherichia coli, even lacking signal peptide affected secretion, obviously inhibited the propagation of EV71 and CA16. Mechanistically, we demonstrated that PF4 blocked the entry of the virus into the host cells by interactions with VP3 proteins of EV71/CA16 and the interaction with SCARB2 receptor-mediated EV71 and CA16 endocytosis. As expected, the incubation of anti-PF4 antibody with PF4 blocked PF4 inhibition on EV71 and CA16 infections further supported the above conclusion. Importantly, pretreatment of EV71 viruses with PF4 significantly protected the neonatal mice from EV71 lethal challenge and promoted the survival rate of infected mice. PF4 derived from natural platelets by EV71/CA16 activation also presented strong inhibition on EV71 and CA16. In summary, our study identified a new host factor against EV71 and CA16 infections, providing a novel strategy for EV71 and CA16 treatment. IMPORTANCE The virus's life cycle starts with binding to cell surface receptors, resulting in receptor-mediated endocytosis. Targeting the entry of the virus into target cells is an effective strategy to develop a novel drug. EV71 and CA16 are the major pathogens that cause hand, foot, and mouth disease (HFMD) outbreaks worldwide since 2008. However, the treatment of EV71 and CA16 infections is mainly symptomatic because there is no approved drug. Therefore, the underlying pathogenesis of EV71/CA16 and the interaction between host-EV71/CA16 need to be further investigated to develop an inhibitor. Here, we identified PF4 as a potent entry inhibitor of EV71 and CA16 via binding to VP3 proteins of EV71 and CA16 or binding to receptor SCARB2. In the EV71 infection model, PF4 protected mice from EV71 lethal challenge and promoted the survival rate of EV71-infected mice. Our study suggests that PF4 represents a potential candidate host factor for anti-EV71 and CA16 infections.

Redox Mechanisms of Platelet Activation in Aging

Aging is intrinsically linked with physiologic decline and is a major risk factor for a broad range of diseases. The deleterious effects of advancing age on the vascular system are evidenced by the high incidence and prevalence of cardiovascular disease in the elderly. Reactive oxygen species are critical mediators of normal vascular physiology and have been shown to gradually increase in the vasculature with age. There is a growing appreciation for the complexity of oxidant and antioxidant systems at the cellular and molecular levels, and accumulating evidence indicates a causal association between oxidative stress and age-related vascular disease. Herein, we review the current understanding of mechanistic links between oxidative stress and thrombotic vascular disease and the changes that occur with aging. While several vascular cells are key contributors, we focus on oxidative changes that occur in platelets and their mediation in disease progression. Additionally, we discuss the impact of comorbid conditions (i.e., diabetes, atherosclerosis, obesity, cancer, etc.) that have been associated with platelet redox dysregulation and vascular disease pathogenesis. As we continue to unravel the fundamental redox mechanisms of the vascular system, we will be able to develop more targeted therapeutic strategies for the prevention and management of age-associated vascular disease.

Effects of room temperature and cold storage on the metabolic and haemostatic properties of whole blood for acute normovolaemic haemodilution

Background

Acute normovolaemic haemodilution (ANH), as a blood-conservation technique, avoids the need for allogeneic blood transfusions. The historic practice of cold-storing type-O whole blood (WB) in military fields popularised the transfusion of refrigerated WB to treat acute bleeding. In this study, we compared the effects of room temperature (RT) and refrigeration up to 24 hours on the coagulation properties of WB for ANH.

Materials and methods

Each WB sample, collected from 12 male volunteers, was divided into two parts, one stored at RT and the other refrigerated for 24 hours. Complete blood counts (CBC), blood gas levels, and coagulation profiles were measured, and rotational thromboelastometry (ROTEM) measurements were performed at the initial collection time point (baseline) and at 6, 12, and 24 hours after initial collection.

Results

The preservation of platelet aggregation response induced by arachidonic acid and adenosine diphosphate was better in cold-stored WB compared to that in RT-stored WB. The platelet aggregation response induced by thrombin receptor-activating peptide 6 was significantly decreased in all samples after 24 hours of storage when compared with that at baseline. The lactate levels in WB stored at RT increased significantly after 6 hours of storage compared to that of cold-stored samples. There were no significant differences in CBC, coagulation parameters, and ROTEM variables between the cold-stored and RT-stored WB samples.

Conclusion

WB for ANH stored in the refrigerator showed better metabolic characteristics after 6 hours of storage and better aggregation response after 12 hours of storage than WB stored at RT.

Models of Shear-Induced Platelet Activation and Numerical Implementation With Computational Fluid Dynamics Approaches

Shear-induced platelet activation is one of the critical outcomes when blood is exposed to elevated shear stress. Excessively activated platelets in the circulation can lead to thrombus formation and platelet consumption, resulting in serious adverse events such as thromboembolism and bleeding. While experimental observations reveal that it is related to the shear stress level and exposure time, the underlying mechanism of shear-induced platelet activation is not fully understood. Various models have been proposed to relate shear stress levels to platelet activation, yet most are modified from the empirically calibrated power-law model. Newly developed multiscale platelet models are tested as a promising approach to capture a single platelet's dynamic shape during activation, but it would be computationally expensive to employ it for a large-scale analysis. This paper summarizes the current numerical models used to study the shear-induced platelet activation and their computational applications in the risk assessment of a particular flow pattern and clot formation prediction.

Bioactive Materials Promote Wound Healing through Modulation of Cell Behaviors

Skin wound repair is a multistage process involving multiple cellular and molecular interactions, which modulate the cell behaviors and dynamic remodeling of extracellular matrices to maximize regeneration and repair. Consequently, abnormalities in cell functions or pathways inevitably give rise to side effects, such as dysregulated inflammation, hyperplasia of nonmigratory epithelial cells, and lack of response to growth factors, which impedes angiogenesis and fibrosis. These issues may cause delayed wound healing or even non-healing states. Current clinical therapeutic approaches are predominantly dedicated to preventing infections and alleviating topical symptoms rather than addressing the modulation of wound microenvironments to achieve targeted outcomes. Bioactive materials, relying on their chemical, physical, and biological properties or as carriers of bioactive substances, can affect wound microenvironments and promote wound healing at the molecular level. By addressing the mechanisms of wound healing from the perspective of cell behaviors, this review discusses how bioactive materials modulate the microenvironments and cell behaviors within the wounds during the stages of hemostasis, anti-inflammation, tissue regeneration and deposition, and matrix remodeling. A deeper understanding of cell behaviors during wound healing is bound to promote the development of more targeted and efficient bioactive materials for clinical applications.

A novel autotransfusion device saving erythrocytes and platelets used in a 72 h survival swine model of surgically induced controlled blood loss

Background

The purpose of this study was to develop a swine model of surgically induced blood loss to evaluate the performances of a new autotransfusion system allowing red blood cells and platelets preservation while collecting, washing and concentrating hemorrhagic blood intraoperatively.

Methods

Two types of surgically induced blood loss were used in 12 minipigs to assess system performance and potential animal complications following autotransfusion: a cardiac model (cardiopulmonary bypass) and a visceral model (induced splenic bleeding). Animal clinical and hematological parameters were evaluated at different time-points from before bleeding to the end of a 72-hour post-transfusion period and followed by a post-mortem examination. System performances were evaluated by qualitative and quantitative parameters.

Results

All animals that received the autotransfusion survived. Minimal variations were seen on the red blood cell count, hemoglobin, hematocrit at the different sampling times. Coagulation tests failed to show any hypo or hypercoagulable state. Gross and histologic examination didn’t reveal any thrombotic lesions. Performance parameters exceeded set objectives in both models: heparin clearance (≥ 90%), final heparin concentration (≤ 0.5 IU/mL), free hemoglobin washout (≥ 90%) and hematocrit (between 45% and 65%). The device treatment rate of diluted blood was over 80 mL/min.

Conclusions

In the present study, both animal models succeeded in reproducing clinical conditions of perioperative cardiac and non-cardiac blood loss. Sufficient blood was collected to allow evaluation of autotransfusion effects on animals and to demonstrate the system performance by evaluating its capacity to collect, wash and concentrate red blood cells and platelets. Reinfusion of the treated blood, containing not only concentrated red blood cells but also platelets, did not lead to any postoperative adverse nor thrombogenic events. Clinical and comparative studies need to be conducted to confirm the clinical benefit of platelet reinfusion.

Platelets after burn injury - hemostasis and beyond

Burn injuries are common and often life-threatening trauma. With this trauma comes an interruption of normal hemostasis, with distinct impacts on platelets. Our interest in the relationships between burn injury and platelet function stems from two key perspectives: platelet function is a vital component of acute responses to injury, and furthermore the incidence of cardiovascular disease (CVD) is higher in burn survivors compared to the general population. This review explores the impact of burn injury on coagulation, platelet function, and the participation of platelets in immunopathology. Potential avenues of further research are explored, and consideration is given to what therapies may be appropriate for mediating post-burn thrombopathology.

Magnitude and Associated Factors of Thrombocytopenia among Pregnant Women Attending Antenatal Care Clinics at Dessie Comprehensive Specialized Hospital, Northeast Ethiopia

BACKGROUND

Thrombocytopenia is a common hematological abnormality during gestation. Pregnant women with severe thrombocytopenia may be associated with a higher risk of excessive bleeding during or after delivery. Therefore, the main aim of this study was to assess the magnitude and associated factors of thrombocytopenia among pregnant women attending antenatal care services at Dessie comprehensive and specialized hospital, Northeast Ethiopia.

METHODS

An institution-based cross-sectional study was conducted from February to March 2021. Using a systematic random sampling technique, a total of 294 pregnant women were enrolled in the study. Structured interviewer-administered questionnaires were used to collect socio-demographic and clinical data of study participants. Four ml of venous blood were collected from each pregnant woman and a complete blood count was determined using DIRUI BF 6500 automated hematology analyzer. Data were entered into Epidata version 4.6.0 and then exported into SPSS version 24.0. Multivariate logistic regression was used to assess the association between dependent and independent variables. P-value < 0.05 was considered to be statistically significant.

RESULTS

A total of 294 pregnant women who visited antenatal care services at Dessie comprehensive specialized hospital were included. The mean (±SD) age of the study participants was 29.7 (±6.1) years. The prevalence of thrombocytopenia among pregnant women was 9.9% (95% CI: 6.5, 13.6). A mild type of thrombocytopenia is the major type and accounted for 72.4% whereas moderate thrombocytopenia and severe thrombocytopenia accounted for 17.2% and 10.4% respectively among pregnant women. Multivariate logistic regression showed that urban residents (AOR: 0.206,95% CI, 0.055-0.748), gestational ages within the first trimester (AOR: 0.183, 95% CI, 0.057-0.593) and gestational ages within the second trimester (AOR = 0.264, 95% CI, 0.092-0.752) were significantly associated and independent predictors of thrombocytopenia in pregnant women.

CONCLUSION

In this study, the prevalence of thrombocytopenia was 9.9% and the mild type of thrombocytopenia (72.4%) was higher than the other type of thrombocytopenia among pregnant women. In multivariate logistic regression analysis, residence and gestational age (trimester) were significantly associated with thrombocytopenia. Therefore, the platelet count should be routinely determined during the antenatal care visit for proper diagnosis and to minimize bleeding during and or after childbirth.

Antioxidant Properties and Structure-Antioxidant Activity Relationship of Allium Species Leaves

Allium is a genus that is widely consumed and used as traditional medicine in several countries. This genus has two major species, namely cultivated species and wild species. Cultivated species consist of A. cepa L., A. sativum L., A. fistulosum L. and A. schoenoprasum L. and wild species consist of A. ursinum L., A. flavum L., A. scorodoprasum L., A. vineale L. and A. atroviolaceum Boiss. Several studies report that the Allium species contain secondary metabolites such as polyphenols, flavonoids and tannins and have bioactivity such as antioxidants, antibacterial, antifungal, anti-inflammatory, pancreatic α-amylase, glucoamylase enzyme inhibitors and antiplatelets. This review summarizes some information regarding the types of Allium species (ethnobotany and ethnopharmacology), the content of compounds of Allium species leaves with various isolation methods, bioactivities, antioxidant properties and the structure-antioxidant activity relationship (SAR) of Allium compounds.

Preparations from selected cucurbit vegetables as antiplatelet agents

Increased blood platelet activation plays an important role in cardiovascular diseases (CVDs). Recent experiments indicate that certain fruits and vegetables, including onion, garlic, and beetroot, have anti-platelet potential and therefore may reduce the likelihood of CVDs. While vegetables from the Cucuritaceae family are known to exerting beneficial antioxidant and anti-inflammatory effects, their effects on blood platelet activation are poorly understood. Therefore, the aim of the present study was to determine the effect on platelet adhesion of preparations from selected cucurbits: pumpkin (Cucurbita pepo; fruit without seeds), zucchini (Cucurbita pepo convar. giromontina; fruit with seeds), cucumber (Cucumis sativus; fruit with seeds), white pattypan squash (Cucurbita pepo var. patisoniana; fruit without seeds) and yellow pattypan squash (Cucurbita pepo var. patisoniana, fruit without seeds). It also evaluates the activity of these preparations on enzymatic lipid peroxidation in thrombin-activated washed blood platelets by TBARS assay. The study also determines the anti-platelet properties of these five cucurbit preparations in whole blood by flow cytometry and with the total thrombus-formation analysis system (T-TAS) and evaluates the cytotoxicity of the tested preparations against platelets based on LDH activity. The results indicate that the yellow Cucurbita pepo var. patisoniana preparation demonstrated stronger anti-platelet properties than the other tested preparations, reducing the adhesion of thrombin-activated platelets to collagen/fibrinogen, and inhibiting arachidonic acid metabolism and GPIIb/IIIa expression on 10 µM ADP-activated platelets. None of the preparations was found to cause platelet lysis. Our findings provide new information on the anti-platelet activity of the tested cucurbit preparations and their potential for treating CVDs associated with platelet hyperactivity.

Preliminary hemocompatibility assessment of an innovative material for blood contacting surfaces

Over the years, several devices have been created (and the development of many others is currently in progress) to be in permanent contact with blood: mechanical circulatory supports represent an example thereof. The hemocompatibility of these devices largely depends on the chemical composition of blood-contacting components. In the present work, an innovative material (hybrid membrane) is proposed to fabricate the inner surfaces of a pulsatile ventricular chamber: it has been obtained by coupling a synthetic polymer (e.g., commercial polycarbonate urethane) with decellularized porcine pericardium. The hemocompatibility of the innovative material has been preliminarily assessed by measuring its capacity to promote thrombin generation and induce platelet activation. Our results demonstrated the blood compatibility of the proposed hybrid membrane.

Current Understanding of the Relationship between Blood Donor Variability and Blood Component Quality

While differences among donors has long challenged meeting quality standards for the production of blood components for transfusion, only recently has the molecular basis for many of these differences become understood. This review article will examine our current understanding of the molecular differences that impact the quality of red blood cells (RBC), platelets, and plasma components. Factors affecting RBC quality include cytoskeletal elements and membrane proteins associated with the oxidative response as well as known enzyme polymorphisms and hemoglobin variants. Donor age and health status may also be important. Platelet quality is impacted by variables that are less well understood, but that include platelet storage sensitive metabolic parameters, responsiveness to agonists accumulating in storage containers and factors affecting the maintenance of pH. An increased understanding of these variables can be used to improve the quality of blood components for transfusion by using donor management algorithms based on a donors individual molecular and genetic profile.

The PI3Kδ Inhibitor Idelalisib Diminishes Platelet Function and Shows Antithrombotic Potential

Background: Clinical management of ischemic events and prevention of vascular disease is based on antiplatelet drugs. Given the relevance of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) as a candidate target in thrombosis, the main goal of the present study was to identify novel antiplatelet agents within the existing inhibitors blocking PI3K isoforms. Methods: We performed a biological evaluation of the pharmacological activity of PI3K inhibitors in platelets. The effect of the inhibitors was evaluated in intracellular calcium release and platelet functional assays, the latter including aggregation, adhesion, and viability assays. The in vivo drug antithrombotic potential was assessed in mice undergoing chemically induced arterial occlusion, and the associated hemorrhagic risk evaluated by measuring the tail bleeding time. Results: We show that PI3K Class IA inhibitors potently block calcium mobilization in human platelets. The PI3K p110δ inhibitor Idelalisib inhibits platelet aggregation mediated by ITAM receptors GPVI and CLEC-2, preferentially by the former. Moreover, Idelalisib also inhibits platelet adhesion and aggregation under shear and adhesion to collagen. Interestingly, an antithrombotic effect was observed in mice treated with Idelalisib, with mild bleeding effects at high doses of the drug. Conclusion: Idelalisib may have antiplatelet effects with minor bleeding effects, which provides a rationale to evaluate its antithrombotic efficacy in humans.

Effects and Side Effects of Platelet Transfusion

Aside from their canonical role in hemostasis, it is increasingly recognized that platelets have inflammatory functions and can regulate both adaptive and innate immune responses. The main topic this review aims to cover is the proinflammatory effects and side effects of platelet transfusion. Platelets prepared for transfusion are subject to stress injury upon collection, preparation, and storage. With these types of stress, they undergo morphologic, metabolic, and functional modulations which are likely to induce platelet activation and the release of biological response modifiers (BRMs). As a consequence, platelet concentrates (PCs) accumulate BRMs during processing and storage, and these BRMs are ultimately transfused alongside platelets. It has been shown that BRMs present in PCs can induce immune responses and posttransfusion reactions in the transfusion recipient. Several recent reports within the transfusion literature have investigated the concept of platelets as immune cells. Nevertheless, current and future investigations will face the challenge of encompassing the immunological role of platelets in the scope of transfusion.

Oxidative Stress Triggers Defective Autophagy in Endothelial Cells: Role in Atherothrombosis Development

Atherothrombosis, a multifactorial and multistep artery disorder, represents one of the main causes of morbidity and mortality worldwide. The development and progression of atherothrombosis is closely associated with age, gender and a complex relationship between unhealthy lifestyle habits and several genetic risk factors. The imbalance between oxidative stress and antioxidant defenses is the main biological event leading to the development of a pro-oxidant phenotype, triggering cellular and molecular mechanisms associated with the atherothrombotic process. The pathogenesis of atherosclerosis and its late thrombotic complications involve multiple cellular events such as inflammation, endothelial dysfunction, proliferation of vascular smooth muscle cells (SMCs), extracellular matrix (ECM) alterations, and platelet activation, contributing to chronic pathological remodeling of the vascular wall, atheromatous plague formation, vascular stenosis, and eventually, thrombus growth and propagation. Emerging studies suggest that clotting activation and endothelial cell (EC) dysfunction play key roles in the pathogenesis of atherothrombosis. Furthermore, a growing body of evidence indicates that defective autophagy is closely linked to the overproduction of reactive oxygen species (ROS) which, in turn, are involved in the development and progression of atherosclerotic disease. This topic represents a large field of study aimed at identifying new potential therapeutic targets. In this review, we focus on the major role played by the autophagic pathway induced by oxidative stress in the modulation of EC dysfunction as a background to understand its potential role in the development of atherothrombosis.

Heterogeneity in Bleeding Tendency and Arthropathy Development in Individuals with Hemophilia

People with hemophilia (PWH) have an increased tendency to bleed, often into their joints, causing debilitating joint disease if left untreated. To reduce the incidence of bleeding events, PWH receive prophylactic replacement therapy with recombinant factor VIII (FVIII) or FIX. Bleeding events in PWH are typically proportional to their plasma FVIII or IX levels; however, in many PWH, bleeding tendency and the likelihood of developing arthropathy often varies independently of endogenous factor levels. Consequently, many PWH suffer repeated bleeding events before correct dosing of replacement factor can be established. Diagnostic approaches to define an individual's bleeding tendency remain limited. Multiple modulators of bleeding phenotype in PWH have been proposed, including the type of disease-causing variant, age of onset of bleeding episodes, plasma modifiers of blood coagulation or clot fibrinolysis pathway activity, interindividual differences in platelet reactivity, and endothelial anticoagulant activity. In this review, we summarize current knowledge of established factors modulating bleeding tendency and discuss emerging concepts of additional biological elements that may contribute to variable bleeding tendency in PWH. Finally, we consider how variance in responses to new gene therapies may also necessitate consideration of patient-specific tailoring of treatment. Cumulatively, these studies highlight the need to reconsider the current "one size fits all" approach to treatment regimens for PWH and consider therapies guided by the bleeding phenotype of each individual PWH at the onset of therapy. Further characterization of the biological bases of bleeding heterogeneity in PWH, combined with the development of novel diagnostic assays to identify those factors that modulate bleeding risk in PWH, will be required to meet these aspirations.

Rho GTPase regulation of reactive oxygen species generation and signalling in platelet function and disease

Platelets are master regulators and effectors of haemostasis with increasingly recognized functions as mediators of inflammation and immune responses. The Rho family of GTPase members Rac1, Cdc42 and RhoA are known to be major components of the intracellular signalling network critical to platelet shape change and morphological dynamics, thus playing a major role in platelet spreading, secretion and thrombus formation. Initially linked to the regulation of actomyosin contraction and lamellipodia formation, recent reports have uncovered non-canonical functions of platelet RhoGTPases in the regulation of reactive oxygen species (ROS), where intrinsically generated ROS modulate platelet function and contribute to thrombus formation. Platelet RhoGTPases orchestrate oxidative processes and cytoskeletal rearrangement in an interconnected manner to regulate intracellular signalling networks underlying platelet activity and thrombus formation. Herein we review our current knowledge of the regulation of platelet ROS generation by RhoGTPases and their relationship with platelet cytoskeletal reorganization, activation and function.

Callicarpa nudiflora Hook. & Arn.: A comprehensive review of its phytochemistry and pharmacology

ETHNOPHARMALOGICAL RELEVANCE

Callicarpa nudiflora Hook. & Arn. is a perennial evergreen shrub or low arbor in the Genus Callicarpa. Its dried aerial parts are used as traditional Chinese herbal medicine, Luo-hua-zi-zhu (Callicarpa nudiflora), which has been widely used in anti-bacteria and anti-ulcer in China (Commission, 2015; Development, 1994; Ming-Sheng, 2008).

AIM OF THE STUDY

The present paper reviewed findings in phytochemistry and pharmacology of Callicarpa nudiflora.

METHODS

Chinese and English studies on Callicarpa nudiflora were collected from databases including Web of Science, SciFinder, PubMed, Elsevier, and CNKI (Chinese), and the phytochemical and pharmacological studies of Callicarpa nudiflora were reviewed.

RESULTS

A total of 300 small molecules, 173 of which are volatile oils, have been isolated from Callicarpa nudiflora. These small molecules could be divided into seven structural types - phenylpropanoids, flavonoids, triterpenes, diterpenes, iridoid glycosides, volatile oils, and other small molecules. Different types of compounds in Callicarpa nudiflora were summarized as follow: a) diterpenoid compounds can inhibit the generation of nitric oxide (NO) for exerting the function of anti-inflammation; b) triterpene compounds can play a role of anti-thrombus via inhibiting platelet aggregation and oleanane type and arbutane type pentacyclic triterpenes have the hepatoprotective activities; c) iridoid glycosides have cytotoxicity to tumor cells, and phenylpropanoids compounds have an antioxidant effect and could improve the function of memory. Our group further studied the antiviral activities of Callicarpa nudiflora finding that it has significant effects on RSV, EV71, COXB5, and HSV-1.

Influence of long-term proteasome inhibition on platelet responsiveness mediated by bortezomib

INTRODUCTION

Although platelets contain a full proteasome system, its role in platelet function is not completely understood yet. Since the proteasome system may be involved in time-delayed processes, platelet responsiveness was investigated after long-term, bortezomib-mediated proteasome inhibition.

MATERIALS AND METHODS

Citrate-anticoagulated whole blood was stored with 5 nM and 1 μM bortezomib for 24 h. Consecutively, aggregation was measured by light transmission in platelet-rich-plasma (PRP). Flow cytometry was performed to determine phosphorylation levels of the vasodilator-stimulated phosphoprotein (VASP), fibrinogen binding, PAC1-antibody binding and purinergic receptor expression in PRP, P2Y12 activity or glycoprotein (GP) Ib and IIb expression in whole blood. P2Y1 and P2X1 activities were assessed by calcium flux-induced fluorescence in washed platelets. Using PRP, adherent platelets on fibrinogen-, collagen- and ristocetin-coated surfaces were visualized and quantified by immunostaining.

RESULTS

Under bortezomib, VASP phosphorylation was less inducible and nitric oxide-induced inhibition of fibrinogen binding was slightly reduced. Proteasome inhibition did not tamper adenosine diphosphate-mediated aggregation or purinergic receptor expression and activity. Induced expression of activated fibrinogen receptors and fibrinogen binding were not significantly influenced by incubation with bortezomib for 24 h. Aggregation values with threshold agonist concentrations were increased under bortezomib. Despite unchanged GPIb expression, bortezomib-treated platelets showed enhanced adhesion on coated surfaces.

CONCLUSIONS

In platelets incubated for 24 h, bortezomib mediates a slight attenuation of inhibitory signaling, associated with facilitated platelet aggregation using threshold agonist concentrations and enhanced adhesion on agonist-coated surfaces.

Characterization of Procoagulant COAT Platelets in Patients with Glanzmann Thrombasthenia

Patients affected by the rare Glanzmann thrombasthenia (GT) suffer from defective or low levels of the platelet-associated glycoprotein (GP) IIb/IIIa, which acts as a fibrinogen receptor, and have therefore an impaired ability to aggregate platelets. Because the procoagulant activity is a dichotomous facet of platelet activation, diverging from the aggregation endpoint, we were interested in characterizing the ability to generate procoagulant platelets in GT patients. Therefore, we investigated, by flow cytometry analysis, platelet functions in three GT patients as well as their ability to generate procoagulant collagen-and-thrombin (COAT) platelets upon combined activation with convulxin-plus-thrombin. In addition, we further characterized intracellular ion fluxes during the procoagulant response, using specific probes to monitor by flow cytometry kinetics of cytosolic calcium, sodium, and potassium ion fluxes. GT patients generated higher percentages of procoagulant COAT platelets compared to healthy donors. Moreover, they were able to mobilize higher levels of cytosolic calcium following convulxin-plus-thrombin activation, which is congruent with the greater procoagulant activity. Further investigations will dissect the role of GPIIb/IIIa outside-in signalling possibly implicated in the regulation of platelet procoagulant activity.

The influence of sodium citrate on the characteristics and biological activity of plasma rich in growth factors

Aim: This study investigated the effect of sodium citrate on the properties and biological activity of plasma rich in growth factors (PRGF). Methods: PRGF was obtained from trisodium citrate and plain extraction tubes. Hematological parameters, growth factors' release kinetics from both PRGF clots and their releasates' biological effect on human bone cells were evaluated. Results: The platelet enrichment factor, the growth factors' content and the release kinetic of PRGF were similar for both groups. The proliferation, collagen type I synthesis and tissue-nonspecific alkaline phosphatase activity of human osteoblasts showed no statistically significant differences. Conclusion: The use of sodium citrate does not influence the composition, the growth factors' release kinetics or the biological effect of PRGF, but it increases its clinical versatility.

Sodium-Calcium Exchanger Reverse Mode Sustains Dichotomous Ion Fluxes Required for Procoagulant COAT Platelet Formation

Procoagulant collagen-and-thrombin (COAT)-activated platelets represent a subpopulation of activated platelets, which retain a coat of prohemostatic proteins and express phosphatidylserine on their surface. Dichotomous intracellular signaling generating procoagulant platelet activity instead of traditional aggregating endpoints is still not fully elucidated. It has been demonstrated that secondary messengers such as calcium and sodium play a critical role in platelet activation. Therefore, we developed a flow cytometric analysis to investigate intracellular ion fluxes simultaneously during generation of aggregating and procoagulant platelets. Human platelets were activated by convulxin-plus-thrombin. Cytosolic calcium, sodium, and potassium ion fluxes were visualized by specific ion probes and analyzed by flow cytometry. We observed high and prolonged intracellular calcium concentration, transient sodium increase, and fast potassium efflux in COAT platelets, whereas aggregating non-COAT platelets rapidly decreased their calcium content, maintaining higher cytosolic sodium, and experiencing lower and slower potassium depletion. Considering these antithetical patterns, we investigated the role of the sodium-calcium exchanger (NCX) during convulxin-plus-thrombin activation. NCX inhibitors, CBDMB and ORM-10103, dose-dependently reduced the global calcium mobilization induced by convulxin-plus-thrombin activation and dose-dependently prevented formation of procoagulant COAT platelets. Our data demonstrate that both NCX modes are used after convulxin-plus-thrombin-induced platelet activation. Non-COAT platelets use forward-mode NCX, thus pumping calcium out and moving sodium in, while COAT platelets rely on reverse NCX function, which pumps additional calcium into the cytosol, by extruding sodium. In conclusion, we described for the first time the critical and dichotomous role of NCX function during convulxin-plus-thrombin-induced platelet activation.

Topology Challenge for the Assessment of Living Cell Deposits with Shear Bulk Acoustic Biosensor

Shear bulk acoustic type of resonant biosensors, such as the quartz crystal microbalance (QCM), give access to label-free in-liquid analysis of surface interactions. The general understanding of the sensing principles was inherited from past developments in biofilms measurements and applied to cells while keeping the same basic assumptions. Thus, the biosensor readouts are still quite often described using 'mass' related terminology. This contribution aims to show that assessment of cell deposits with acoustic biosensors requires a deep understanding of the sensor transduction mechanism. More specifically, the cell deposits should be considered as a structured viscoelastic load and the sensor response depends on both material and topological parameters of the deposits. This shifts the paradigm of acoustic biosensor away from the classical mass loading perspective. As a proof of the concept, we recorded QCM frequency shifts caused by blood platelet deposits on a collagen surface under different rheological conditions and observed the final deposit shape with atomic force microscopy (AFM). The results vividly demonstrate that the frequency shift is highly impacted by the platelet topology on the bio-interface. We support our findings with numerical simulations of viscoelastic unstructured and structured loads in liquid. Both experimental and theoretical studies underline the complexity behind the frequency shift interpretation when acoustic biosensing is used with cell deposits.

Role of Platelet Cytokines in Dengue Virus Infection

Platelets are anucleated blood cells derived from bone marrow megakaryocytes and play a crucial role in hemostasis and thrombosis. Platelets contain specialized storage organelles, called alpha-granules, contents of which are rich in cytokines such as C-X-C Motif Chemokine Ligand (CXCL) 1/4/7, (C-C motif) ligand (CCL) 5/3, CXCL8 (also called as interleukin 8, IL-8), and transforming growth factor β (TGF-β). Activation of platelets lead to degranulation and release of contents into the plasma. Platelet activation is a common event in many viral infections including human immunodeficiency virus (HIV), H1N1 influenza, Hepatitis C virus (HCV), Ebola virus (EBV), and Dengue virus (DENV). The cytokines CXCL8, CCL5 (also known as Regulated on Activation, Normal T Expressed and Secreted, RANTES), tumor necrosis factor α (TNF-α), CXCL1/5 and CCL3 released, promote development of a pro-inflammatory state along with the recruitment of other immune cells to the site of infection. Platelets also interact with Monocytes and Neutrophils and facilitate their activation to release different cytokines which further enhances inflammation. Upon activation, platelets also secrete factors such as CXCL4 (also known as platelet factor, PF4), CCL5 and fibrinopeptides which are critical regulators of replication and propagation of several viruses in the host. Studies suggest that CXCL4 can both inhibit as well as enhance HIV1 infection. Data from our lab show that CXCL4 inhibits interferon (IFN) pathway and promotes DENV replication in monocytes in vitro and in patients significantly. Inhibition of CXCL4 mediated signaling results in increased IFN production and suppressed DENV and JEV replication in monocytes. In this review, we discuss the role of platelets in viral disease progression with a focus on dengue infection.

Aedes albopictus D7 Salivary Protein Prevents Host Hemostasis and Inflammation

Mosquitoes inject saliva into the host skin to facilitate blood meal acquisition through active compounds that prevent hemostasis. D7 proteins are among the most abundant components of the mosquito saliva and act as scavengers of biogenic amines and eicosanoids. Several members of the D7 family have been characterized at the biochemical level; however, none have been studied thus far in Aedes albopictus, a permissive vector for several arboviruses that causes extensive human morbidity and mortality. Here, we report the binding capabilities of a D7 long form protein from Ae. albopictus (AlboD7L1) by isothermal titration calorimetry and compared its model structure with previously solved D7 structures. The physiological function of AlboD7L1 was demonstrated by ex vivo platelet aggregation and in vivo leukocyte recruitment experiments. AlboD7L1 binds host hemostasis agonists, including biogenic amines, leukotrienes, and the thromboxane A2 analog U-46619. AlboD7L1 protein model predicts binding of biolipids through its N-terminal domain, while the C-terminal domain binds biogenic amines. We demonstrated the biological function of AlboD7L1 as an inhibitor of both platelet aggregation and cell recruitment of neutrophils and eosinophils. Altogether, this study reinforces the physiological relevance of the D7 salivary proteins as anti-hemostatic and anti-inflammatory molecules that help blood feeding in mosquitoes.

Catestatin prevents endothelial inflammation and promotes thrombus resolution in acute pulmonary embolism in mice

Catestatin (CTS), a catecholamine-release inhibitory peptide, exerts pleiotropic cardiac protective effects. Pulmonary embolism caused by deep vein thrombosis involving vascular dysfunction. The present study aims to investigate the effects of CTS on thrombus formation that may inhibit the development of pulmonary embolism and its potential pathway. Acute pulmonary embolism (APE) model was developed as an in vivo model. The effects of CTS on mice with APE were examined. Human pulmonary artery endothelial cells (HPAECs) were pretreated with CTS before thrombin stimulation, and endothelial inflammation and underlying mechanisms were evaluated in vitro. That plasma CTS level was decreased in APE mice, while the number of platelets was significantly increased. The decreased circulating CTS level negatively associated with the number of platelets. CTS administration increased the survival rate of APE mice and protected against microvascular thrombosis in lung. APE-induced the increase in platelets number and plasma von Willebrand factor (VWF) were inhibited by CTS. Platelets from CTS-treated APE mice showed impaired agonist-induced platelets aggregation and spreading. CTS also ameliorated APE-induced the systemic inflammatory response. In in vivo study, thrombin-induced the increase in inflammation, TLR-4 expression and p38 phosphorylation were abrogated by CTS in HPAECs. Furthermore, TLR-4 overexpression inhibited the effect of CTS on VWF release and inflammation in HPAECs. Collectively, CTS increases thrombus resolution by attenuating endothelial inflammation at partially via inhibiting TLR-4-p38 pathway. The present study may provide a novel approach for anti-thrombosis.

Brucella abortus-infected platelets modulate the activation of neutrophils

Brucellosis is a contagious disease caused by bacteria of the genus Brucella. Platelets (PLTs) have been widely involved in the modulation of the immune response. We have previously reported the modulation of Brucella abortus-mediated infection of monocytes. As a result, PLTs cooperate with monocytes and increase their inflammatory capacity, promoting the resolution of the infection. Extending these results, in this study we demonstrate that patients with brucellosis present slightly elevated levels of complexes between PLTs and both monocytes and neutrophils. We then assessed whether PLTs were capable of modulating functional aspects of neutrophils. The presence of PLTs throughout neutrophil infection increased the production of interleukin-8, CD11b surface expression and reactive oxygen species formation, whereas it decreased the expression of CD62L, indicating an activated status of these cells. We next analyzed whether this modulation was mediated by released factors. To discriminate between these options, neutrophils were treated with supernatants collected from B. abortus-infected PLTs. Our results show that CD11b expression was induced by soluble factors of PLTs but direct contact between cell populations was needed to enhance the respiratory burst. Additionally, B. abortus-infected PLTs recruit polymorphonuclear (PMN) cells to the site of infection. Finally, the presence of PLTs did not modify the initial invasion of PMN cells by B. abortus but improved the control of the infection at extended times. Altogether, our results demonstrate that PLTs interact with neutrophils and promote a proinflammatory phenotype which could also contribute to the resolution of the infection.

The TICONC (Ticagrelor-Oncology) Study: Implications of P2Y12 Inhibition for Metastasis and Cancer-Associated Thrombosis

Background

In cancer, platelets may facilitate metastatic spread by a number of mechanisms as well as contribute to thrombotic complications. Ticagrelor, a platelet antagonist- that blocks adenosine diphosphate activation of platelet P2Y₁₂ receptors, is widely used in the treatment of cardiovascular disease, but its efficacy in cancer remains unknown.

Objectives

This study sought to evaluate the effect of aspirin and ticagrelor monotherapy, as well as dual antiplatelet therapy, on platelet activation in cancer.

Methods

This study consisted of 2 phases: first, an in vitro study of human platelet−tumor cell interaction; and second, a randomized crossover clinical trial of 22 healthy donors and 16 patients with metastatic breast or colorectal cancer. Platelet activation and inhibition were measured by aggregometry and flow cytometry.

Results

In vitro, tumor cells induced cellular clusters that were predominantly platelet−platelet aggregates. Ticagrelor significantly inhibited formation of large tumor cell-induced platelet−platelet aggregates: 65.4 ± 4.8% to 50.9 ± 5.9% (p = 0.002) and 62.3 ± 3.1% to 48.3 ± 7.3% (p = 0.014) for MCF-7 and HT-29-induced aggregation, respectively. Supporting this finding, cancer patients on ticagrelor had significantly reduced levels of spontaneous platelet aggregation and activation compared with baseline; 14.8 ± 2.7% at baseline to 7.8 ± 2.3% with ticagrelor (p = 0.012).

Conclusions

Our findings suggested that P2Y₁₂ inhibition with ticagrelor might reduce spontaneous platelet aggregation and activation in patients with metastatic cancer and merits further investigation in patients at high risk of cancer-associated thrombosis. (Ticagrelor-Oncology [TICONC] Study; EudraCT: 2014-004049-29)

ADP binding by the Culex quinquefasciatus mosquito D7 salivary protein enhances blood feeding on mammals

During blood-feeding, mosquito saliva is injected into the skin to facilitate blood meal acquisition. D7 proteins are among the most abundant components of the mosquito saliva. Here we report the ligand binding specificity and physiological relevance of two D7 long proteins from Culex quinquefasciatus mosquito, the vector of filaria parasites or West Nile viruses. CxD7L2 binds biogenic amines and eicosanoids. CxD7L1 exhibits high affinity for ADP and ATP, a binding capacity not reported in any D7. We solve the crystal structure of CxD7L1 in complex with ADP to 1.97 Å resolution. The binding pocket lies between the two protein domains, whereas all known D7s bind ligands either within the N- or the C-terminal domains. We demonstrate that these proteins inhibit hemostasis in ex vivo and in vivo experiments. Our results suggest that the ADP-binding function acquired by CxD7L1 evolved to enhance blood-feeding in mammals, where ADP plays a key role in platelet aggregation.

D7 proteins are highly abundant in the salivary glands of several blood feeding insects. Here, the authors study the ligand binding specificity and physiological roles of the mosquito D7 proteins CxD7L1 and CxD7L2, showing that CxD7L1 acquired ADP-binding properties to enhance blood feeding in mammals.

Pathophysiology of the Venous Thromboembolism Risk in Preeclampsia

Preeclampsia complicates up to 8% of pregnancies and is a leading cause of fetomaternal morbidity andmortality. Treatment options are limited, with supportive care and delivery of the placenta representing the cornerstone of current management strategies. Derangements in blood coagulation are wellrecognised in this disorder and appear to favour an increased risk of venous thromboembolism among affected women. This risk appears to be most significant in the postpartum period. The mechanisms underlying this increased thrombosis risk remain to be fully elucidated although increased expression of procoagulant factors, endothelial dysfunction, attenuation of endogenous anticoagulant activity and increased platelet activity have been implicated in the prothrombotic tendency. Preeclampsia is also occasionally complicated by life-threatening haemorrhagic events and current evidence suggests that in some severe manifestations of this disease a coagulopathy with a clinical bleeding tendency may be the predominant haemostatic abnormality. Identifying affected women at significant risk of thrombosis and managing the competing thrombotic and haemorrhagic risks continue to be a significant clinical challenge. Derangements in blood coagulation are also implicated in the pathogenesis of preeclampsia; however, the role of antiplatelet or anticoagulant drugs in the prevention and treatment of this disorder remains a source of considerable debate. In addition, the potential role of specific haemostatic markers as diagnostic or screening tools for preeclampsia has also yet to be determined. Further characterisation of the underlying molecular mechanisms would likely be of major translational relevance and could provide insights into the pathogenesis of this disease as well as the associated haemostatic dysfunction.

A biomimetic platelet based on assembling peptides initiates artificial coagulation

Platelets play a critical role in the regulation of coagulation, one of the essential processes in life, attracting great attention. However, mimicking platelets for in vivo artificial coagulation is still a great challenge due to the complexity of the process. Here, we design platelet-like nanoparticles (pNPs) based on self-assembled peptides that initiate coagulation and form clots in blood vessels. The pNPs first bind specifically to a membrane glycoprotein (i.e., CD105) overexpressed on angiogenetic endothelial cells in the tumor site and simultaneously transform into activated platelet-like nanofibers (apNFs) through ligand-receptor interactions. Next, the apNFs expose more binding sites and recruit and activate additional pNPs, forming artificial clots in both phantom and animal models. The pNPs are proven to be safe in mice without systemic coagulation. The self-assembling peptides mimic platelets and achieve artificial coagulation in vivo, thus providing a promising therapeutic strategy for tumors.