ROS scavenger, N-acetyl-l-cysteine and NOX specific inhibitor, VAS2870 reduce platelets apoptosis while enhancing their viability during storage

Impact of 6-hydroxydopamine on agonist-induced human platelet functional parameters: An explanation for platelet impairment in Parkinson's disease

Parkinson's disease (PD) is the second-most prevalent neurodegenerative disease worldwide, which worsens with advancing age. It is a common movement disorder and is often associated with several vascular diseases with decreased stroke frequency. Circulating platelets substantially regulate vascular complications, including stroke, and share striking similarities with PD neurons. Although structural alterations in platelets are well-documented in PD, their functional parameters remain unclear. This study aimed to investigate the functional abnormalities in platelets associated with PD by evaluating key functional aspects such as adhesion, activation, secretion, aggregation, and clot retraction. To achieve this, we treated human blood platelets with 6-hydroxydopamine or 6-OHDA, that selectively destroys dopaminergic neurons, thereby creating an in vitro experimental model that closely resembles the pathogenic environment in PD, and examine its impact on platelet functions. In our study, platelet adhesion was assessed and further evaluated by a microplate reader, activation and secretion by a flow cytometer, aggregation by aggregometer, and clot retraction by Sonoclot. Phase-contrast and confocal microscopic studies further verified the results from the above experiments. Our findings showed that 6-OHDA treatment significantly inhibited thrombin (a platelet agonist)-induced functions, including adhesion, activation, aggregation, secretion, and clot retraction in human-washed platelets. In summary, this research provides pioneering evidence that 6-OHDA induces abnormal platelet functions, shedding light on the previously unexplored processes by which 6-OHDA affects platelet activity.

Lysophosphatidylcholine induces oxidative stress and calcium-mediated cell death in human blood platelets

Platelets are essential component of circulation that plays a major role in hemostasis and thrombosis. During activation and its demise, platelets release platelet-derived microvesicles, with lysophosphatidylcholine (LPC) being a prominent component in their lipid composition. LPC, an oxidized low-density lipoprotein, is involved in cellular metabolism, but its higher level is implicated in pathologies like atherosclerosis, diabetes, and inflammatory disorders. Despite this, its impact on platelet function remains relatively unexplored. To address this, we studied LPC's effects on washed human platelets. A multimode plate reader was employed to measure reactive oxygen species and intracellular calcium using H2DCF-DA and Fluo-4-AM, respectively. Flow cytometry was utilized to measure phosphatidylserine expression, mitochondrial membrane potential (ΔΨm), and mitochondrial permeability transition pore (mPTP) formation using FITC-Annexin V, JC-1, and CoCl2/calcein-AM, respectively. Additionally, platelet morphology and its ultrastructure were observed via phase contrast and electron microscopy. Sonoclot and light transmission aggregometry were employed to examine fibrin formation and platelet aggregation, respectively. The findings demonstrate that LPC induced oxidative stress and increased intracellular calcium in platelets, resulting in increased phosphatidylserine expression and reduced ΔΨm. LPC triggered caspase-independent platelet death and mPTP opening via cytosolic and mitochondrial calcium, along with microvesiculation and reduced platelet counts. LPC increased the platelet's size, adopting a balloon-shaped morphology, causing membrane fragmentation and releasing its cellular contents, while inducing a pro-coagulant phenotype with increased fibrin formation and reduced integrin αIIbβ3 activation. Conclusively, this study reveals LPC-induced oxidative stress and calcium-mediated platelet death, necrotic in nature with pro-coagulant properties, potentially impacting inflammation and repair mechanisms during vascular injury.

Fibrinogen binding to activated platelets and its biomimetic thrombus-targeted thrombolytic strategies

Thrombosis is associated with various fatal arteriovenous syndromes including ischemic stroke, myocardial infarction, and pulmonary embolism. However, current clinical thrombolytic treatment strategies still have many problems in targeting and safety to meet the thrombolytic therapy needs. Understanding the molecular mechanism that underlies thrombosis is critical in developing effective thrombolytic strategies. It is well known that platelets play a central role in thrombosis and the binding of fibrinogen to activated platelets is a common pathway in the process of clot formation. Based on this, a concept of biomimetic thrombus-targeted thrombolytic strategy inspired from fibrinogen binding to activated platelets in thrombosis was proposed, which could selectively bind to activated platelets at a thrombus site, thus enabling targeted delivery and local release of thrombolytic agents for effective thrombolysis. In this review, we first summarized the main characteristics of platelets and fibrinogen, and then introduced the classical molecular mechanisms of thrombosis, including platelet adhesion, platelet activation and platelet aggregation through the interactions of activated platelets with fibrinogen. In addition, we highlighted the recent advances in biomimetic thrombus-targeted thrombolytic strategies which inspired from fibrinogen binding to activated platelets in thrombosis. The possible future directions and perspectives in this emerging area are briefly discussed.

Investigating the role of rotenone on human blood platelets: Molecular insights into abnormal platelet functions in Parkinson's disease

Parkinson's disease (PD) is a predominant neuromotor disorder characterized by the selective death of dopaminergic neurons in the midbrain. The majority of PD cases are sporadic or idiopathic, with environmental toxins and pollutants potentially contributing to its development or exacerbation. However, clinical PD patients are often associated with a reduced stroke frequency, where circulating blood platelets are indispensable. Although platelet structural impairment is evident in PD, the platelet functional alterations and their underlying molecular mechanisms are still obscure. Therefore, we investigated rotenone (ROT), an environmental neurotoxin that selectively destroys dopaminergic neurons mimicking PD, on human blood platelets to explore its impact on platelet functions, thus replicating PD conditions in vitro. Our study deciphered that ROT decreased thrombin-induced platelet functions, including adhesion, activation, secretion, and aggregation in human blood platelets. As ROT is primarily responsible for generating intracellular reactive oxygen species (ROS), and ROS is a key player regulating the platelet functional parameters, we went on to check the effect of ROT on platelet ROS production. In our investigation, it became evident that ROT treatment resulted in the stimulation of ROS production in human blood platelets. Additionally, we discovered that ROT induced ROS production by augmenting Ca2+ mobilization from inositol 1,4,5-trisphosphate receptor. Apart from this, the treatment of ROT triggers protein kinase C associated NADPH oxidase-mediated ROS production in platelets. In summary, this research, for the first time, highlights ROT-induced abnormal platelet functions and may provide a mechanistic insight into the altered platelet activities observed in PD patients.

The platelet storage lesion, what are we working for?

BACKGROUND

Platelet concentrate (PC) transfusions are crucial in prevention and treatment of bleeding in infection, surgery, leukemia, and thrombocytopenia patients. Although the technology for platelet preparation and storage has evolved over the decades, there are still challenges in the demand for platelets in blood banks because the platelet shelf life is limited to 5 days due to bacterial contamination and platelet storage lesions (PSLs) at 20-24°C under constant horizontal agitation. In addition, the relations between some adverse effects of platelet transfusions and PSLs have also been considered. Therefore, understanding the mechanisms of PSLs is conducive to obtaining high quality platelets and facilitating safe and effective platelet transfusions.

OBJECTIVE

This review summarizes developments in mechanistic research of PSLs and their relationship with clinical practice, providing insights for future research.

METHODS

Authors conducted a search on PubMed and Web of Science using the professional terms "PSL" and "platelet transfusion." The obtained literature was then roughly categorized based on their research content. Similar studies were grouped into the same sections, and further searches were conducted based on the keywords of each section.

RESULTS

Different studies have explored PSLs from various perspectives, including changes in platelet morphology, surface molecules, biological response modifiers (BMRs), metabolism, and proteins and RNA, in an attempt to monitor PSLs and identify intervention targets that could alleviate PSLs. Moreover, novel platelet storage conditions, including platelet additive solutions (PAS) and reconsidered cold storage methods, are explored. There are two approaches to obtaining high-quality platelets. One approach simulates the in vivo environment to maintain platelet activity, while the other keeps platelets at a low activity level in vitro under low temperatures.

CONCLUSION

Understanding PSLs helps us identify good intervention targets and assess the therapeutic effects of different PSLs stages for different patients.

Platelets and the Atherosclerotic Process: An Overview of New Markers of Platelet Activation and Reactivity, and Their Implications in Primary and Secondary Prevention

The key role played by platelets in the atherosclerosis physiopathology, especially in the acute setting, is ascertained: they are the main actors during thrombus formation and, thus, one of the major investigated elements related to atherothrombotic process involving coronary arteries. Platelets have been studied from different points of view, according with the technology advances and the improvement in the hemostasis knowledge achieved in the last years. Morphology and reactivity constitute the first aspects investigated related to platelets with a significant body of evidence published linking a number of their values and markers to coronary artery disease and cardiovascular events. Recently, the impact of genetics on platelet activation has been explored with promising findings as additional instrument for patient risk stratification; however, this deserves further confirmations. Moreover, the interplay between immune system and platelets has been partially elucidated in the last years, providing intriguing elements that will be basic components for future research to better understand platelet regulation and improve cardiovascular outcome of patients.

Novel Strategies in the Early Detection and Treatment of Endothelial Cell-Specific Mitochondrial Dysfunction in Coronary Artery Disease

Although elevated cholesterol and other recognised cardiovascular risk factors are important in the development of coronary artery disease (CAD) and heart attack, the susceptibility of humans to this fatal process is distinct from other animals. Mitochondrial dysfunction of cells in the arterial wall, particularly the endothelium, has been strongly implicated in the pathogenesis of CAD. In this manuscript, we review the established evidence and mechanisms in detail and explore the potential opportunities arising from analysing mitochondrial function in patient-derived cells such as endothelial colony-forming cells easily cultured from venous blood. We discuss how emerging technology and knowledge may allow us to measure mitochondrial dysfunction as a potential biomarker for diagnosis and risk management. We also discuss the "pros and cons" of animal models of atherosclerosis, and how patient-derived cell models may provide opportunities to develop novel therapies relevant for humans. Finally, we review several targets that potentially alleviate mitochondrial dysfunction working both via direct and indirect mechanisms and evaluate the effect of several classes of compounds in the cardiovascular context.

CD30 induces Reed-Sternberg cell-like morphology and chromosomal instability in classic Hodgkin lymphoma cell lines

Classic Hodgkin lymphoma (cHL) is characterized by multinucleated cells called Reed-Sternberg (RS) cells and genetic complexity. Although CD30 also characterizes cHL cells, its biological roles are not fully understood. In this report, we examined the link between CD30 and these characteristics of cHL cells. CD30 stimulation increased multinucleated cells resembling RS cells. We found chromatin bridges, a cause of mitotic errors, among the nuclei of multinucleated cells. CD30 stimulation induced DNA double-strand breaks (DSBs) and chromosomal imbalances. RNA sequencing showed significant changes in the gene expression by CD30 stimulation. We found that CD30 stimulation increased intracellular reactive oxygen species (ROS), which induced DSBs and multinucleated cells with chromatin bridges. The PI3K pathway was responsible for CD30-mediated generation of multinucleated cells by ROS. These results suggest that CD30 involves generation of RS cell-like multinucleated cells and chromosomal instability through induction of DSBs by ROS, which subsequently induces chromatin bridges and mitotic error. The results link CD30 not only to the morphological features of cHL cells, but also to the genetic complexity, both of which are characteristic of cHL cells.

Myocardial ischemia-reperfusion injury; Molecular mechanisms and prevention

Cardiovascular diseases are one of the leading causes of mortality in developed countries. Among cardiovascular disorders, myocardial infarction remains a life-threatening problem predisposing to the development and progression of ischemic heart failure. Ischemia/reperfusion (I/R) injury is a critical cause of myocardial injury. In recent decades, many efforts have been made to find the molecular and cellular mechanisms underlying the development of myocardial I/R injury and post-ischemic remodeling. Some of these mechanisms are mitochondrial dysfunction, metabolic alterations, inflammation, high production of ROS, and autophagy deregulation. Despite continuous efforts, myocardial I/R injury remains a major challenge in medical treatments of thrombolytic therapy, heart disease, primary percutaneous coronary intervention, and coronary arterial bypass grafting. The development of effective therapeutic strategies to reduce or prevent myocardial I/R injury is of great clinical significance.

Unveiling the mechanism of platelet dysfunction in Parkinson's disease: The effect of 6-hydroxydopamine on human blood platelets

INTRODUCTION

Parkinson's disease (PD) is a progressive neuronal illness often linked to increased cardiovascular complications, such as myocardial infarction, cardiomyopathy, congestive heart failure, and coronary heart disease. Platelets, which are the essential components of circulating blood, are considered potential players in regulating these complications, as platelet dysfunction is evident in PD. These tiny blood cell fragments are supposed to play a crucial role in these complications, but the underlying molecular processes are still obscure.

METHODS

To gain a better understanding of platelet dysfunction in PD, we investigated the impact of 6-hydroxydopamine (6-OHDA), an analog of dopamine that simulates PD by destroying dopaminergic neurons, on human blood platelets. The levels of intraplatelet reactive oxygen species (ROS) were assessed using H₂DCF-DA (20 μM), while mitochondrial ROS was evaluated using MitoSOX™ Red (5 μM), and intracellular Ca²⁺ was measured with Fluo-4-AM (5 μM). The data were acquired through the use of both a multimode plate reader and a laser-scanning confocal microscope.

RESULTS

Our findings showed that 6-OHDA treatment increased the production of ROS in human blood platelets. The increase in ROS was confirmed by the ROS scavenger, NAC, and was also reduced by inhibiting the NOX enzyme with apocynin. Additionally, 6-OHDA potentiated mitochondrial ROS production in platelets. Furthermore, 6-OHDA triggered the intraplatelet Ca²⁺ elevation. This effect was mitigated by the Ca²⁺ chelator BAPTA, which decreased the ROS production triggered by 6-OHDA in human blood platelets, while the IP₃ receptor blocker, 2-APB, reduced the formation of ROS induced by 6-OHDA.

CONCLUSION

Our findings suggest that the 6-OHDA-induced ROS production is regulated by the IP₃ receptor-Ca²⁺-NOX signaling axis in human blood platelets, where the platelet mitochondria also play a significant role. This observation provides a crucial mechanistic understanding of the altered platelet activities that are commonly observed in PD patients.

Gamma irradiation induces a pro-apoptotic state in longer stored platelets, without progressing to an overt apoptosis by day 7 of storage

BACKGROUND

Although gamma-irradiation to platelet products is a standard method to prevent the risk of TA-GVHD in vulnerable recipients, it induces some proteomic and redox changes, of which irradiation-induced ROS increments may potentiate platelet mitochondrial dysfunction. However, whether these changes cause platelet apoptosis, or affect their viability during storage, is the main subject of this study.

METHODS

PLT-rich plasma PC was split into two bags, one kept as control while other was subjected to gamma-irradiation. Within 7-days storage, cytosolic and mitochondrial levels of cytochrome c and pro-apoptotic molecules of Bak and Bax were evaluated by western-blotting. Intraplatelet active caspase (using FAM-DEVD-FMK) and PS-exposure were detected by flowcytometry. Caspase activity in platelet lysate was also confirmed by immunofluorescence detection of Caspase-3/7 Substrate N-Ac-DEVD-N'-MC-R110 while platelet viability was evaluated with MTT assays.

RESULTS

Cytosolic cytochrome c gradually increased while its mitochondrial content steadily declined during 7 days of storage. In a contrary trend, reverse patterns were observed for Bak and Bax expressions. Gamma-irradiated platelets showed higher release of mitochondrial cytochrome c that reflected by higher cytosolic cytochrome c levels on day 7 of storage. Concurrently mitochondrial pro-apoptotic Bak and Bax proteins increased on day 7 in irradiated products. However, gamma-irradiation didn't significantly increase caspase activity or PS-exposure, nor did it decrease platelet viability.

CONCLUSION

Here, consistent with studies on "gamma-irradiation-induced oxidative stress", we showed that gamma-ray also increases platelet pro-apoptotic signals during storage, although not strongly enough to affect platelet viability by overt apoptosis induction. Conclusively, whether supplementing ROS scavengers or antioxidants to irradiated platelets can improve their quality during storage may be of interest for future research.

Research progress on the interaction between oxidative stress and platelets: Another avenue for cancer?

Oxidative stress (OS) is a chemical imbalance between an oxidant and an antioxidant, causing damage to redox signaling and control or causing molecular damage. Unbalanced oxidative metabolism can produce excessive reactive oxygen species (ROS). These excess ROS can cause drastic changes in platelet metabolism and further affect platelet function. It will also lead to an increase in platelet procoagulant phenotype and cell apoptosis, which will increase the risk of thrombosis. The creation of ROS and subsequent platelet activation, adhesion, and recruitment are then further encouraged in an auto-amplifying loop by ROS produced from platelets. Meanwhile, cancer cells produce a higher concentration of ROS due to their fast metabolism and high proliferation rate. However, excessive ROS can result in damage to and modification of cellular macromolecules. The formation of cancer and its progression is strongly associated with oxidative stress and the resulting oxidative damage. In addition, platelets are an important part of the tumor microenvironment, and there is a significant cross-communication between platelets and cancer cells. Cancer cells alter the activation status of platelets, their RNA spectrum, proteome, and other properties. The "cloaking" of cancer cells by platelets providing physical protection，avoiding destruction from shear stress and the attack of immune cells, promoting tumor cell invasion.We explored the vicious circle interaction between ROS, platelets, and cancer in this review, and we believe that ROS can play a stimulative role in tumor growth and metastasis through platelets.

CD30 stimulation induces multinucleation and chromosomal instability in HTLV-1-infected cell lines

A recent report indicated involvement of CD30 in progression of human leukemia virus type 1 (HTLV-1) infection, but the exact roles of CD30 in this process remain unclear. This study was conducted to determine the role of CD30 by stimulating CD30 expressed on HTLV-1-infected cell lines with CD30 ligand and observing its effects. CD30 stimulation increased multinucleated cells and inhibited proliferation of HTLV-1-infected cells. This inhibition was recovered by interruption of CD30 stimulation. Chromatin bridges found in multinucleated cells suggested DNA damage. CD30 stimulation triggered DNA double-strand breaks (DSBs) and chromosomal imbalances. CD30 stimulation induced reactive oxygen species (ROS), which induced DSBs. Generation of ROS and multinucleated cells by CD30 was dependent on phosphoinositide 3-kinase. RNA sequencing showed that CD30 stimulation produced significant changes in gene expression profiles, including upregulation of programmed death ligand 1 (PD-L1). Tax, which has also been shown to induce multinucleation and chromosomal instability, failed to induce CD30. These results suggest that induction of CD30, independent of Tax, triggers morphological abnormalities, chromosomal instability, and alteration of gene expression in HTLV-1-infected cells.

Novel roles for HMGA2 isoforms in regulating oxidative stress and sensitizing to RSL3-Induced ferroptosis in prostate cancer cells

Oxidative stress is increased in several cancers including prostate cancer, and is currently being exploited in cancer therapy to induce ferroptosis, a novel nonapoptotic form of cell death. High mobility group A2 (HMGA2), a non-histone protein up-regulated in several cancers, can be truncated due to chromosomal rearrangement or alternative splicing of HMGA2 gene. The purpose of this study is to investigate the role of wild-type vs. truncated HMGA2 in prostate cancer (PCa). We analyzed the expression of wild-type vs. truncated HMGA2 and showed that prostate cancer patient tissue and some cell lines expressed increasing amounts of both wild-type and truncated HMGA2 with increasing tumor grade, compared to normal epithelial cells. RNA-Seq analysis of LNCaP prostate cancer cells stably overexpressing wild-type HMGA2 (HMGA2-WT), truncated HMGA2 (HMGA2-TR) or empty vector (Neo) control revealed that HMGA2-TR cells exhibited higher oxidative stress compared to HMGA2-WT or Neo control cells, which was also confirmed by analysis of basal reactive oxygen species (ROS) levels using 2', 7'-dichlorofluorescin diacetate (DCFDA) dye, the ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) and NADP/NADPH using metabolomics. This was associated with increased sensitivity to RAS-selective lethal 3 (RSL3)-induced ferroptosis that could be antagonized by ferrostatin-1. Additionally, proteomic and immunoprecipitation analyses showed that cytoplasmic HMGA2 protein interacted with Ras GTPase-activating protein-binding protein 1 (G3BP1), a cytoplasmic stress granule protein that responds to oxidative stress, and that G3BP1 transient knockdown increased sensitivity to ferroptosis even further. Endogenous knockdown of HMGA2 or G3BP1 in PC3 cells reduced proliferation which was reversed by ferrostatin-1. In conclusion, we show a novel role for HMGA2 in oxidative stress, particularly the truncated HMGA2, which may be a therapeutic target for ferroptosis-mediated prostate cancer therapy.

Platelets Facilitate Wound Healing by Mitochondrial Transfer and Reducing Oxidative Stress in Endothelial Cells

As a critical member in wound healing, vascular endothelial cells (ECs) impaired under high levels of reactive oxygen species (ROS) would hamper neovascularization. Mitochondria transfer can reduce intracellular ROS damage under pathological condition. Meanwhile, platelets can release mitochondria and alleviate oxidative stress. However, the mechanism by which platelets promote cell survival and reduce oxidative stress damage has not been clarified. Here, first, we selected ultrasound as the best method for subsequent experiments by detecting the growth factors and mitochondria released from manipulation platelet concentrates (PCs), as well as the effect of manipulation PCs on the proliferation and migration of HUVECs. Then, we found that sonicate platelet concentrates (SPC) decreased the level of ROS in HUVECs treated with hydrogen peroxide in advance, increased mitochondrial membrane potential, and reduced apoptosis. By transmission electron microscope, we saw that two kinds of mitochondria, free or wrapped in vesicles, were released by activated platelets. In addition, we explored that platelet-derived mitochondria were transferred to HUVECs partly by means of dynamin-dependent clathrin-mediated endocytosis. Consistently, we determined that platelet-derived mitochondria reduced apoptosis of HUVECs caused by oxidative stress. What is more, we screened survivin as the target of platelet-derived mitochondria via high-throughput sequencing. Finally, we demonstrated that platelet-derived mitochondria promoted wound healing in vivo. Overall, these findings revealed that platelets are important donors of mitochondria, and platelet-derived mitochondria can promote wound healing by reducing apoptosis caused by oxidative stress in vascular endothelial cells. And survivin is a potential target. These results further expand the knowledge of the platelet function and provide new insights into the role of platelet-derived mitochondria in wound healing.

Evaluation of Platelet Parameters in Patients With Secondary Failure of Platelet Recovery and Cytomegalovirus Infection After Hematopoietic Stem Cell Transplantation

OBJECTIVE

To investigate the clinical significance of changes in platelet parameters in patients with secondary failure of platelet recovery (SFPR) and cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT).

METHODS

In this retrospective study, 79 patients who had undergone allogeneic HSCT (allo-HSCT), including 40 patients with SFPR and 39 patients without SFPR, were recruited. The evaluated parameters were platelet count (PLT), plateletcrit (PCT), platelet-large cell ratio (P-LCR), mean platelet volume (MPV), platelet distribution width (PDW), the incidence of CMV infection after allo-HSCT, and the correlation of SFPR and CMV infection in patients who had undergone allo-HSCT. The control group included 107 healthy donors.

RESULTS

The SFPR group had significantly lower megakaryocyte counts, PLT, and PCT and significantly higher P-LCR, MPV, and PDW than the healthy donor and non-SFPR groups. The incidence of CMV infection was higher in SFPR patients than in non-SFPR patients. Among the patients with SFPR, P-LCR, MPV, and PDW were lower in those with CMV DNA >8000 copies/mL than in those with CMV DNA <8000 copies/mL (P < .05 for all); the CMV viral load was slightly negatively correlated with MPV (P = .0297) and P-LCR (P = .0280).

CONCLUSION

We demonstrate for the first time that the level of platelet activation in SFPR patients, which was closely related to CMV infection, was higher than that in that in non-SFPR patients, and higher CMV load was associated with the inhibition of platelet activation.

Improvement of platelet preservation by inhibition of TRPC6

BACKGROUND

The preservation of platelets (PLTs) by room temperature (RT) oscillation limits their shelf life to between 4 and 7 days because of the decrease in PLT function. TRPC6 is a non-selective mechanically sensitive cation channel that has been shown to mediate Ca²⁺ signalling, implying a role in PLT activation during preservation by RT oscillation.

OBJECTIVES

This study was designed to investigate whether inhibition of TRPC6 can improve the RT preservation of PLTs and the possible underlying mechanism.

METHODS

Human PLTs from whole blood were stored at 22 ± 2°C with oscillation in plasma or M-sol (mixture of solutions). BI-749327, a specific TRPC6 inhibitor, was administered throughout the preservation period. PLT distribution width (PDW), mean platelet volume (MPV), maximum platelet aggregation rate (MAR) and average aggregation rate (AAR) were measured. The MTT method was used to assess the relative viability of PLTs. Flow cytometry was used to measure the changes of Ca²⁺ concentration in PLTs and phosphatidylserine (PS) exposure on the PLT surface, and western blotting was used to assess the expression changes of platelet TRPC6 and CD62P proteins.

RESULTS

Compared with the control group, inhibition of TRPC6 with BI-749327 significantly reduced the PDW, MPV and Ca²⁺ concentration, the MAR and AAR were significantly increased, the expression of TRPC6 and CD62P protein was significantly down-regulated in PLTs, and the PS exposure was significantly reduced on the PLT surface. However, these effects were all reversed by activation of TRPC6.

CONCLUSION

Inhibition of TRPC6 improves the quality of PLT preservation by inhibiting the Ca²⁺ signal mediated by TRPC6.

Platelet storage: Progress so far

There is a crucial need for platelet transfusion during an emergency-surgery and treatment of platelet disorders. The unavailability of donors has furthermore increased the demand for platelet storage. Platelets have limited shelf life due to bacterial contamination and storage lesions. Temperature, materials, oxygen availability, media, platelet processing and manufacturing methods influence the platelet quality and viability during storage. The conception of various platelet additive solutions along with the advent of plastic storage during the 1980s led to enormous developments in platelet storage strategies. Cold storage of platelets gained attention despite its inability to contribute to platelet survival post-transfusion as it offers faster haemostasis. Several developments in platelet storage strategies over the years have improved the quality and shelf-life of stored platelets. Despite the progress, the efficacy of platelets during storage beyond a week has not been achieved. Antioxidants as additives have been explored in platelet storage and have proven to enhance the efficacy of platelets during prolonged storage. However, the molecular interactions of antioxidants in platelets can provide a better understanding of their mechanism of action. Optimization of dosage concentrations of antioxidants is also a critical parameter to be considered as they tend to exhibit toxicity at certain levels. This review provides comprehensive insights into the critical factors affecting platelet storage and the evolution of platelet storage. It also emphasizes the role of antioxidants as additives in platelet storage solutions and their future prospects towards better platelet banking.

Aza-BODIPY based carbonic anhydrase IX: Strategy to overcome hypoxia limitation in photodynamic therapy

Hypoxia caused by photodynamic therapy (PDT) is a major hurdle to cancer treatment since it can promote recurrence and progression by activating angiogenic factors, lowering therapeutic efficacy dramatically. In this work, AZB-I-CAIX₂ was developed as a carbonic anhydrase IX (CAIX)-targeting NIR photosensitizer that can overcome the challenge by utilizing a combination of CAIX knockdown and PDT. AZB-I-CAIX₂ showed a specific affinity to CAIX-expressed cancer cells and enhanced photocytotoxicity compared to AZB-I-control (the molecule without acetazolamide). Moreover, selective detection and effective cell cytotoxicity of AZB-I-CAIX₂ by PDT in hypoxic CAIX-expressed murine cancer cells were achieved. Essentially, AZB-I-CAIX₂ could minimize tumor size in the tumor-bearing mice compared to that in the control groups. The results suggested that AZB-I-CAIX₂ can improve therapeutic efficiency by preventing PDT-induced hypoxia through CAIX inhibition.

Targeting biophysical cues to address platelet storage lesions

Platelets play vital roles in vascular repair, especially in primary hemostasis, and have been widely used in transfusion to prevent bleeding or manage active bleeding. Recently, platelets have been used in tissue repair (e.g., bone, skin, and dental alveolar tissue) and cell engineering as drug delivery carriers. However, the biomedical applications of platelets have been associated with platelet storage lesions (PSLs), resulting in poor clinical outcomes with reduced recovery, survival, and hemostatic function after transfusion. Accumulating evidence has shown that biophysical cues play important roles in platelet lesions, such as granule secretion caused by shear stress, adhesion affected by substrate stiffness, and apoptosis caused by low temperature. This review summarizes four major biophysical cues (i.e., shear stress, substrate stiffness, hydrostatic pressure, and thermal microenvironment) involved in the platelet preparation and storage processes, and discusses how they may synergistically induce PSLs such as platelet shape change, activation, apoptosis and clearance. We also review emerging methods for studying these biophysical cues in vitro and existing strategies targeting biophysical cues for mitigating PSLs. We conclude with a perspective on the future direction of biophysics-based strategies for inhibiting PSLs. STATEMENT OF SIGNIFICANCE: Platelet storage lesions (PSLs) involve a series of structural and functional changes. It has long been accepted that PSLs are initiated by biochemical cues. Our manuscript is the first to propose four major biophysical cues (shear stress, substrate stiffness, hydrostatic pressure, and thermal microenvironment) that platelets experience in each operation step during platelet preparation and storage processes in vitro, which may synergistically contribute to PSLs. We first clarify these biophysical cues and how they induce PSLs. Strategies targeting each biophysical cue to improve PSLs are also summarized. Our review is designed to draw the attention from a broad range of audience, including clinical doctors, biologists, physical scientists, engineers and materials scientists, and immunologist, who study on platelets physiology and pathology.

Erythrocyte Storage Lesion Improvements Mediated by Naringin Screened from Vegetable/Fruit Juice Using Cell Extract and HPLC-MS

In blood banking, storage at 4°C for weeks is known to cause damages to erythrocytes, called storage lesions that may later cause transfusion-related adverse events. In previous experiments, we found that vegetable/fruit juices can effectively reduce the storage lesion. Currently, we attempt to analyze the potential bioactive components and test whether the compounds can improve the storage lesions of erythrocytes. Equal portions in wet weight of 20 fresh vegetables and fruits were blended with phosphate buffered solution (PBS), and clear solutions were produced as additive to the packed erythrocytes from consented blood donors at 1 : 10 ratio (ml : gram). The blood samples were stored for 35 days at 4°C, and the supernatants were performed high liquid chromatography-mass spectrometry (HPLC-MS) analysis at 0 days, 14 days, and 35 days. The blood bags supplemented with identified bioactive components were stored in a refrigerator for 35 days, and the morphology, complete blood count (CBC), phosphatidylserine (PS) extroversion, hemolysis, and reactive oxygen species (ROS) levels were measured at the end of storage. Five potential bioactive components from vegetable/fruit juices contributed to the improvements of storage lesion. One of the compounds was unequivocally identified as naringin, and two were tentatively assigned as vitexin 6″-O-malonyl 2″-O-xyloside and luteolin 7-(6″-malonyl neohesperidoside). Naringin alleviated the storage lesion of red blood cells (RBCs) by reducing ROS levels and living cell extraction with HPLC-MS is a simple, reliable, and effective method for screening potential bioactive components.

Autophagy Ameliorates Reactive Oxygen Species-Induced Platelet Storage Lesions

Platelet transfusion is a life-saving therapy to prevent bleeding; however, the availability of platelets for transfusion is limited by the markedly short shelf life owing to the development of platelet storage lesions (PSLs). The mechanism of PSLs remains obscure. Dissection of the intracellular biological changes in stored platelets may help to reduce PSLs and improve platelet transfusion efficiency. In the present study, we explore the changes of stored platelets at room temperature under constant agitation. We found that platelets during storage showed an increased reactive oxygen species (ROS) generation accompanied with receptor shedding, apoptosis, and diminished platelet aggregation. ROS scavenger reduced platelet shedding but also impaired platelet aggregation. Autophagy is a conserved catabolic process that sequesters protein aggregates and damaged organelles into lysosomes for degradation and platelets’ own intact autophagic system. We revealed that there exist a stable autophagic flux in platelets at the early stage of storage, and the autophagic flux in platelets perished after long-term storage. Treatment stored platelets with rapamycin, which stimulates autophagy in eukaryotic cells, markedly ameliorated PSLs, and improved platelet aggregation in response to extracellular stimuli.

Assessment of apheresis platelets during 5 days of storage: A National Cancer Institute, Cairo University experience

BACKGROUND

Platelet transfusion therapy is widely used to prevent hemorrhage in patients with thrombocytopenia and platelet disorders. The platelet concentrate (PC) quality is affected by increased storage time, as reflected in the decreased number of platelets, morphological changes, and impaired functions. This study aimed to analyze the impact of 5 days storage on platelets count and the expression of CD63, and Annexin V as activation markers during PC storage.

METHODS

Fifty PCs collected from single donors were tested for platelet count on days 0, 3, and 5 using a Sysmex blood counter. CD61, CD63, and Annexin V expression was analyzed by a multicolor Navios flow cytometer.

RESULTS

There was a significant decrease in platelet count during 5 days of storage. There was a direct relationship between storage time and degree of platelet activation. CD63 had almost double increased expression on day 5 than day 3. Annexin V showed significantly increased expression on day 3 with minor differences between days 3 and 5.

CONCLUSION

According to standard blood bank conditions, PC stored for 5 days showed a degree of in vitro activation as evidenced by CD63 and Annexin V expression, may lead to reduced therapeutic efficacy. Flow cytometry monitoring platelet activation in PC offers a better understanding of the changes during PC storage and may help improve platelet products.

Irradiation of platelets in Transfusion Medicine: risk and benefit judgments

Irradiation of platelet products is generally used to prevent transfusion-associated graft-versus-host disease (TA-GvHD) as well as transfusion-transmitted infections. As an essential prerequisite, gamma-irradiation of blood products prior to transfusion is required in patients who may develop TA-GVHD. Most studies suggest that gamma irradiation has no significant effect on the quality of platelet products; however, more recent studies have shown that the oxidative effects of gamma irradiation can lead to the induction of platelet storage lesion (PSL) and to some extent reduce the efficiency of transfused platelets. As the second widely used irradiation technique, UV-illumination was primarily introduced to reduce the growth of infectious agents during platelet storage, with the advantage that this method can also prevent TA-GvHD. However, the induction of oxidative conditions and platelet pre-activation that lead to PSL is more pronounced after UV-based methods of pathogen reduction. Since these lesions are large enough to clearly affect the post-transfusion platelet recovery and survival, more studies are needed to improve the safety and effectiveness of pathogen reduction technologies (PRTs). Therefore, pointing to other benefits of PRTs, such as preventing TA-GvHD or prolonging the shelf life of products by eliminating the possibility of pathogen growth during storage, does not yet seem to justify their widespread use due to above-mentioned effects. Even for gamma-irradiated platelets, some researchers have suggested that due to decreased 1-hour post-transfusion increments and increased risk of platelet refractoriness, their use should be limited to the patients who may develop TA-GVHD. It is noteworthy that due to the effect of X-rays in preventing TA-GvHD, some recent studies are underway to examine its effects on the quality and effectiveness of platelet products and determine whether X-rays can be used as a more appropriate and cost-effective alternative to gamma radiation. The review presented here provides a detailed description about irradiation-based technologies for platelet products, including their applications, mechanistic features, advantages, and disadvantages.

NP-ALT, a Liposomal:Peptide Drug, Blocks p27Kip1 Phosphorylation to Induce Oxidative Stress, Necroptosis, and Regression in Therapy-Resistant Breast Cancer Cells

Resistance to cyclin D-CDK4/6 inhibitors (CDK4/6i) represents an unmet clinical need and is frequently caused by compensatory CDK2 activity. Here we describe a novel strategy to prevent CDK4i resistance by using a therapeutic liposomal:peptide formulation, NP-ALT, to inhibit the tyrosine phosphorylation of p27Kip1(CDKN1B), which in turn inhibits both CDK4/6 and CDK2. We find that NP-ALT blocks proliferation in HR+ breast cancer cells, as well as CDK4i-resistant cell types, including triple negative breast cancer (TNBC). The peptide ALT is not as stable in primary mammary epithelium, suggesting that NP-ALT has little effect in nontumor tissues. In HR+ breast cancer cells specifically, NP-ALT treatment induces ROS and RIPK1-dependent necroptosis. Estrogen signaling and ERα appear required. Significantly, NP-ALT induces necroptosis in MCF7 ESR^Y537S cells, which contain an ER gain of function mutation frequently detected in metastatic patients, which renders them resistant to endocrine therapy. Here we show that NP-ALT causes necroptosis and tumor regression in treatment naïve, palbociclib-resistant, and endocrine-resistant BC cells and xenograft models, demonstrating that p27 is a viable therapeutic target to combat drug resistance. IMPLICATIONS: This study reveals that blocking p27 tyrosine phosphorylation inhibits CDK4 and CDK2 activity and induces ROS-dependent necroptosis, suggesting a novel therapeutic option for endocrine and CDK4 inhibitor-resistant HR+ tumors.

NADPH Oxidases Are Required for Full Platelet Activation In Vitro and Thrombosis In Vivo but Dispensable for Plasma Coagulation and Hemostasis

OBJECTIVE

Using 3KO (triple NOX [NADPH oxidase] knockout) mice (ie, NOX1-/-/NOX2-/-/NOX4-/-), we aimed to clarify the role of this family of enzymes in the regulation of platelets in vitro and hemostasis in vivo. Approach and Results: 3KO mice displayed significantly reduced platelet superoxide radical generation, which was associated with impaired platelet aggregation, adhesion, and thrombus formation in response to the key agonists collagen and thrombin. A comparison with single-gene knockouts suggested that the phenotype of 3KO platelets is the combination of the effects of the genetic deletion of NOX1 and NOX2, while NOX4 does not show any significant function in platelet regulation. 3KO platelets displayed significantly higher levels of cGMP-a negative platelet regulator that activates PKG (protein kinase G). The inhibition of PKG substantially but only partially rescued the defective phenotype of 3KO platelets, which are responsive to both collagen and thrombin in the presence of the PKG inhibitors KT5823 or Rp-8-pCPT-cGMPs, but not in the presence of the NOS (NO synthase) inhibitor L-NG-monomethyl arginine. In vivo, triple NOX deficiency protected against ferric chloride-driven carotid artery thrombosis and experimental pulmonary embolism, while hemostasis tested in a tail-tip transection assay was not affected. Procoagulatory activity of platelets (ie, phosphatidylserine surface exposure) and the coagulation cascade in platelet-free plasma were normal.

CONCLUSIONS

This study indicates that inhibiting NOXs has strong antithrombotic effects partially caused by increased intracellular cGMP but spares hemostasis. NOXs are, therefore, pharmacotherapeutic targets to develop new antithrombotic drugs without bleeding side effects.

Antioxidant prevents clearance of hemostatically competent platelets after long-term cold storage

BACKGROUND

Cold storage of platelets (PLTs) has the potential advantage of prolonging storage time while reducing posttransfusion infection given the decreased likelihood of bacterial outgrowth during storage and possibly beneficial effects in treating bleeding patients. However, cold storage reduces PLT survival through the induction of complex storage lesions, which are more accentuated when storage is prolonged.

STUDY DESIGN AND METHODS

Whole blood-derived PLT-rich plasma concentrates from seven PLT pools (n = 5 donors per pool). PLT additive solution was added (67%/33% plasma) and the product was split into 50-mL bags. Split units were stored in the presence or absence of 1 mM of N-acetylcysteine (NAC) under agitation for up to 14 days at room temperature or in the cold and were analyzed for PLT activation, fibrinogen-dependent spreading, microparticle formation, mitochondrial respiratory activity, reactive oxygen species (ROS) generation, as well as in vivo survival and bleeding time correction in immunodeficient mice.

RESULTS

Cold storage of PLTs for 7 days or longer induces significant PLT activation, cytoskeletal damage, impaired fibrinogen spreading, enhances mitochondrial metabolic decoupling and ROS generation, and increases macrophage-dependent phagocytosis and macrophage-independent clearance. Addition of NAC prevents PLT clearance and allows a correction of the prolonged bleeding time in thrombocytopenic, aspirin-treated, immunodeficient mice.

CONCLUSIONS

Long-term cold storage induces mitochondrial uncoupling and increased proton leak and ROS generation. The resulting ROS is a crucial contributor to the increased macrophage-dependent and -independent clearance of functional PLTs and can be prevented by the antioxidant NAC in a magnesium-containing additive solution.

The effect of gamma irradiation on platelet redox state during storage

BACKGROUND

As a method with insignificant adverse effects on in vitro quality of platelet concentrates (PCs), gamma irradiation is applied to abrogate the risk of transfusion-associated graft-vs-host disease in vulnerable recipients. However, there is some evidence of lower posttransfusion responses and proteomic alterations in gamma-irradiated platelets (PLTs), which raises some questions about their quality, safety, and efficacy. Since reactive oxygen species (ROS) are considered as markers of PLT storage lesion (PSL), the study presented here investigated oxidant state in gamma-irradiated PCs.

STUDY DESIGN AND METHODS

PLT-rich plasma PC was split into two bags, one kept as control while other was subjected to gamma irradiation. Within 7 days of storage, the levels of intra-PLT superoxide, H₂ O₂ , mitochondrial ROS, P-selectin expression, and phosphatidylserine (PS) exposure were detected by flow cytometry while intracellular reduced glutathione (GSH), glucose concentration, and lactate dehydrogenase (LDH) activity were measured by enzymocolorimetric method.

RESULTS

GSH decreased, while ROS generation and LDH activity increased, during storage. Gamma irradiation significantly attenuated GSH whereas increased ROS generation in earlier and later stages of storage associated with either P-selectin or PS exposure increments.

CONCLUSION

Gamma irradiation can significantly increase cytosolic ROS generation in two distinct phases, one upon irradiation and another later in longer-stored PCs. While earlier ROS influx seems to be governed by direct effect of irradiation, the second phase of oxidant stress is presumably due to the storage-dependent PLT activation. Intriguingly, these observations were also in line with early P-selectin increments and increased PS exposure in longer-stored PLTs. Given the mutual link between ROS generation and PLT activation, further investigation is required to explore the effect of gamma irradiation on the induction of PSL.

GPX3 methylation is associated with hematologic improvement in low-risk myelodysplastic syndrome patients treated with Pai-Neng-Da

Objective

The aim of this prospective randomized controlled clinical trial was to explore the relationship between GPX3 methylation and Pai-Neng-Da (PND) in the treatment of patients with low-risk myelodysplastic syndrome (MDS).

Methods

There were 82 low-risk MDS patients who were randomly divided into the following two groups: androl, thalidomide, and PND capsule (ATP group, n = 41); or androl and thalidomide (AT group, n = 41). Hemoglobin and neutrophil and platelet counts and changes in GPX3 methylation level were assessed.

Results

The plasma hemoglobin level increased in both groups after treatment. However, the platelet count increased only in the ATP group. Patients in the ATP group had a better platelet response than the AT group, and GPX3 methylation markedly decreased after treatment with ATP but not after treatment with AT. Moreover, male patients had a significantly lower GPX3 methylation level than female patients, while platelet counts from male patients increased dramatically after the ATP regimens compared with female patients. GPX3 methylation changes were negatively correlated with platelet changes in ATP group.

Conclusion

PND can improve hematological parameters and decrease the GPX3 methylation level. Decreasing GPX3 methylation is associated with the hematologic response that includes platelet in GPX3 methylation.

China Clinical Trial Bureau (ChiCTR;http://www.chictr.org.cn/) registration number: ChiCTR-IOR-15006635.

Collagen-dependent platelet dysfunction and its relevance to either mitochondrial ROS or cytosolic superoxide generation: a question about the quality and functional competence of long-stored platelets

Background

Upon vascular damage, the exposed subendothelial matrix recruits circulating platelets to site of injury while inducing their firm adhesion mainly via GPVI-collagen interaction. GPVI also supports aggregatory and pro-coagulant functions in arterial shear rate even on the matrix other than collagen. Reactive oxygen species (ROS) modulate these stages of thrombosis; however augmented oxidant stress also disturbs platelet functions. Stored-dependent platelet lesion is associated with the increasing levels of ROS. Whether ROS accumulation is also relevant to collagen-dependent platelet dysfunction is the main interest of this study.

Methods

Fresh PRP-PCs (platelet concentrates) were either stimulated with potent ROS-inducers PMA and CCCP or stored for 5 days. Intra-platelet superoxide (O₂ ^--) or mitochondrial-ROS and GPVI expression were detected by flowcytometery. GPVI shedding, platelet aggregation and spreading/adhesion to collagen were analyzed by western blot, aggregometry and fluorescence-microscopy, respectively.

Results

Mitochondrial-ROS levels in 5 days-stored PCs were comparable to those induced by mitochondrial uncoupler, CCCP while O₂ ^-- generations were higher than those achieved by PMA. Shedding levels in 5 days-stored PCs were higher than those induced by these potent stimuli. GPVI expressions were reduced comparably in CCCP treated and 5 days-stored PCs. Platelet adhesion was also diminished during storage while demonstrating significant reverse correlation with GPVI shedding. However, only firm adhesion (indicated by platelets spreading or adhesion surface area) was relevant to GPVI expression. Platelet adhesion and aggregation also showed reverse correlations with both O2^-- and mitochondrial-ROS formations; nonetheless mitochondrial-ROS was only relevant to firm adhesion.

Conclusion

As a sensitive indicator of platelet activation, GPVI shedding was correlated with either simple adhesion or spreading to collagen, while GPVI expression was only relevant to platelet spreading. Thereby, if the aim of GPVI evaluation is to examine platelet firm adhesion, expression seems to be a more specific choice. Furthermore, the comparable levels of ROS generation in 5 days-stored PCs and CCCP treated platelets, indicated that these products are significantly affected by oxidative stress. Reverse correlation of accumulating ROS with collagen-dependent platelet dysfunction is also a striking sign of an oxidant-induced lesion that may raise serious question about the post-transfusion quality and competence of longer-stored platelet products.

Compound Prunetin Induces Cell Death in Gastric Cancer Cell with Potent Anti-Proliferative Properties: In Vitro Assay, Molecular Docking, Dynamics, and ADMET Studies

Gastric cancer is the common type of malignancy positioned at second in mortality rate causing burden worldwide with increasing treatment options. Prunetin (PRU) is an O-methylated flavonoid that belongs to the group of isoflavone executing beneficial activities. In the present study, we investigated the anti-proliferative and cell death effect of the compound PRU in AGS gastric cancer cell line. The in vitro cytotoxic potential of PRU was evaluated and significant proliferation was observed. We identified that the mechanism of cell death was due to necroptosis through double staining and was confirmed by co-treatment with inhibitor necrostatin (Nec-1). We further elucidated the mechanism of action of necroptosis via receptor interacting protein kinase 3 (RIPK3) protein expression and it has been attributed by ROS generation through JNK activation. Furthermore, through computational analysis by molecular docking and dynamics simulation, the efficiency of compound prunetin against RIPK3 binding was validated. In addition, we also briefed the pharmacokinetic properties of the compound by in silico ADMET analysis.

Reducing state attenuates ectodomain shedding of GPVI while restoring adhesion capacities of stored platelets: evidence addressing the controversy around the effects of redox condition on thrombosis

Thrombosis involves different stages including platelet adhesion to the site of injury, aggregatory events governed by integrin activation, pro-inflammatory responses recruiting leukocytes and finally, pro-coagulant activity which results in fibrin generation and clot formation. As important signaling agents, reactive oxygen species (ROS) reduce thrombus volume and growth, however given such a multistage mechanism, it is not well-elucidated how ROS inhibition modulates thrombosis. PRP-platelet concentrates (PCs) were either treated with ROS-reducing agents (1 mM NAC or 30 μM NOX inhibitor, VAS2870) or kept untreated during storage. Shedding and expression of platelet adhesion receptors in presence of inhibitors, agonists and CCCP (as controls) were analyzed by flow cytometery and western blot respectively. Besides above parameters, platelet adhesion to collagen in stored platelets was examined in presence of ROS inhibitors using fluorescence-microscopy. Highest levels of adhesion receptors shedding were achieved by ionophore and CCCP while collagen induces much more GPVI shedding than that of GPIbα. ROS inhibition reduced receptors shedding from day 3 of storage while enhanced their expressions. ROS inhibition not only did not reduce platelet adhesion capacity but it also enhanced platelets adhesion (in presence of NAC) or spreading (in presence of VAS2870) in 5 days-stored PCs. While reducing state significantly inhibits platelet aggregation and thrombus growth, our results indicated that as a first stage of thrombosis, platelet adhesion is resistance to such inhibitory effects. These findings highlight the fact that integrin-dependent platelet activation is much more vulnerable to the inhibition of ROS generation than GPVI-dependent platelet adhesion. Presumably, inhibition of platelet activating signals by ROS inhibitors preserves platelet adhesiveness to collagen due to lessening GPVI shedding.

The impact of bilirubin ditaurate on platelet quality during storage

Bilirubin ditaurate (BRT), a conjugated bilirubin analogue, has demonstrated anti-platelet characteristics following acute ex vivo exposure. Scavenging of mitochondrial superoxide and attenuation of granule exocytosis suggested a potential benefit for including BRT for storage. With no reports of cytotoxicity following acute exposure, the impact of 35µM BRT on platelet function was investigated, in clinically suppled units, for up to seven days. Exposure to 35µM BRT significantly reduced mitochondrial membrane potential and increased glucose consumption until exhaustion after 72 hours. Platelet aggregation and activation was significantly impaired by BRT. Mitochondrial superoxide production and phosphatidylserine expression were significantly elevated following glucose exhaustion, with decreased viability observed from day five onwards. Lactate accumulation and loss of bicarbonate, support a metabolic disturbance, leading to a decline of quality following BRT inclusion. Although acute ex vivo BRT exposure reported potentially beneficial effects, translation from acute to chronic exposure failed to combat declining platelet function during storage. BRT exposure resulted in perturbations of platelet quality, with the utility of BRT during storage therefore limited. However, these are the first data of prolonged platelet exposure to analogues of conjugated bilirubin and may improve our understanding of platelet function in the context of conjugated hyperbilirubinemia.

Acute bilirubin ditaurate exposure attenuates ex vivo platelet reactive oxygen species production, granule exocytosis and activation

Background

Bilirubin, a by-product of haem catabolism, possesses potent endogenous antioxidant and platelet inhibitory properties. These properties may be useful in inhibiting inappropriate platelet activation and ROS production; for example, during storage for transfusion. Given the hydrophobicity of unconjugated bilirubin (UCB), we investigated the acute platelet inhibitory and ROS scavenging ability of a water-soluble bilirubin analogue, bilirubin ditaurate (BRT) on ex vivo platelet function to ascertain its potential suitability for inclusion during platelet storage.

Methods

The inhibitory potential of BRT (10–100 μM) was assessed using agonist induced platelet aggregation, dense granule exocytosis and flow cytometric analysis of P-selectin and GPIIb/IIIa expression. ROS production was investigated by analysis of H₂DCFDA fluorescence following agonist simulation while mitochondrial ROS production investigated using MitoSOX™ Red. Platelet mitochondrial membrane potential and viability was assessed using TMRE and Zombie Green™ respectively.

Results

Our data shows ≤35 μM BRT significantly inhibits both dense and alpha granule exocytosis as measured by ATP release and P-selectin surface expression, respectively. Significant inhibition of GPIIb/IIIa expression was also reported upon ≤35 μM BRT exposure. Furthermore, platelet exposure to ≤10 μM BRT significantly reduces platelet mitochondrial ROS production. Despite the inhibitory effect of BRT, platelet viability, mitochondrial membrane potential and agonist induced aggregation were not perturbed.

Conclusions

These data indicate, for the first time, that BRT, a water-soluble bilirubin analogue, inhibits platelet activation and reduces platelet ROS production ex vivo and may, therefore, may be of use in preserving platelet function during storage.

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The impact of conjugated bilirubin on platelet function has not been investigated to date.

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Bilirubin ditaurate (BDT) is a water-soluble analogue of conjugated bilirubin.

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BDT attenuates ex vivo platelet activation and ROS generation.

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Conjugated forms of bilirubin might inhibit platelet activation during storage.

VAS2870 Inhibits Histamine-Induced Calcium Signaling and vWF Secretion in Human Umbilical Vein Endothelial Cells

In this study, we investigated the effects of NAD(P)H oxidase (NOX) inhibitor VAS2870 (3-benzyl-7-(2-benzoxazolyl)thio-1,2,3-triazolo[4,5-d]pyrimidine) on the histamine-induced elevation of free cytoplasmic calcium concentration ([Ca²⁺]_i) and the secretion of von Willebrand factor (vWF) in human umbilical vein endothelial cells (HUVECs) and on relaxation of rat aorta in response to histamine. At 10 μM concentration, VAS2870 suppressed the [Ca²⁺]_i rise induced by histamine. Inhibition was not competitive, with IC50 3.64 and 3.22 μM at 1 and 100 μM concentrations of histamine, respectively. There was no inhibition of [Ca²⁺]_i elevation by VAS2870 in HUVECs in response to the agonist of type 1 protease-activated receptor SFLLRN. VAS2870 attenuated histamine-induced secretion of vWF and did not inhibit basal secretion. VAS2870 did not change the degree of histamine-induced relaxation of rat aortic rings constricted by norepinephrine. We suggest that NOX inhibitors might be used as a tool for preventing thrombosis induced by histamine release from mast cells without affecting vasorelaxation.