The protective effects of paclitaxel on platelet aggregation through the inhibition of thromboxane A2 synthase

Antiplatelet, cytotoxic activities and characterization of green-synthesized zinc oxide nanoparticles using aqueous extract of Nephrolepis exaltata

The goal of the current study was to synthesize zinc oxide nanoparticles (ZnO-NPs) using ZnCl₂.2H₂O salt precursor and an aqueous extract of Nephrolepis exaltata (N. exaltata), which act as a capping and reducing agent. N. exaltata plant extract-mediated ZnO-NPs were further characterized by various techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), UV-visible (UV-Vis), and energy-dispersive X-ray (EDX) analysis. The nanoscale crystalline phase of ZnO-NPs was analyzed by the XRD patterns. The FT-IR analysis revealed different functional groups of biomolecules involved in the reduction and stabilization of the ZnO-NPs. The light absorption and optical properties of ZnO-NPs were examined by UV-Vis spectroscopy at a wavelength of 380 nm. The spherical shape morphology of ZnO-NPs with mean particle size ranges between 60 and 80 nm was confirmed by SEM images. While the EDX analysis was used to identify the elemental composition of ZnO-NPs. Furthermore, the synthesized ZnO-NPs demonstrate potential antiplatelet activity by inhibiting the platelet aggregation induced by platelet activation factor (PAF) and arachidonic acid (AA). The results showed that synthesized ZnO-NPs were more effective in inhibiting platelet aggregation induced by AA with IC₅₀ (56% and 10 μg/mL) and PAF (63% and 10 μg/mL), respectively. However, the biocompatibility of ZnO-NPs was assessed in human lung cancer cell line (A549) under in vitro conditions. The cytotoxicity of synthesized nanoparticles revealed that cell viability decreased and the IC₅₀ was found to be 46.7% at a concentration of 75 μg/mL. The present work concluded the green synthesis of ZnO-NPs that was achieved by N. exaltata plant extract and showed good antiplatelet and cytotoxic activity, which demonstrates the lack of harmful effects making them more effective for use in pharmaceutical and medical fields to treat thrombotic disorders.

Paclitaxel exerts antiplatelet and antithrombotic activities: Additional benefit from use of paclitaxel-coated balloons and -eluting stents in coronary revascularization and prevention of in-stent restenosis

INTRODUCTION

Paclitaxel is a microtubule-stabilizing drug used to treat several types of cancer, including ovarian and breast cancer. Because of its antiproliferative effect on vascular smooth muscle cells, balloons and stents are coated with paclitaxel for use in coronary revascularization and prevention of in-stent restenosis (ISR). However, mechanisms underlying ISR are complicated. Platelet activation is one of the major causes of ISR after percutaneous coronary intervention. Although the antiplatelet activity of paclitaxel was noted in rabbit platelets, the effect of paclitaxel on platelets remains unclear. This study investigated whether paclitaxel exhibits antiplatelet activity in human platelets.

METHODS AND RESULTS

Paclitaxel inhibited platelet aggregation induced by collagen but not that induced by thrombin, arachidonic acid, or U46619, suggesting that paclitaxel is more sensitive to the inhibition of collagen-induced platelet activation. Moreover, paclitaxel blocked collagen receptor glycoprotein (GP) VI downstream signaling molecules, including Lyn, Fyn, PLCγ2, PKC, Akt, and MAPKs. However, paclitaxel did not directly bind to GPVI and cause GPVI shedding, as detected by surface plasmon resonance and flow cytometry, respectively, indicating that paclitaxel may interfere with GPVI downstream signaling molecules, such as Lyn and Fyn. Paclitaxel also prevented granule release and GPIIbIIIa activation induced by collagen and low convulxin doses. Moreover, paclitaxel attenuated pulmonary thrombosis and delayed platelet thrombus formation in mesenteric microvessels without significantly affecting hemostasis.

CONCLUSION

Paclitaxel exerts antiplatelet and antithrombotic effects. Thus, paclitaxel may provide additional benefits beyond its antiproliferative effect when used in drug-coated balloons and drug-eluting stents for coronary revascularization and prevention of ISR.

Design of a Platelet-Mediated Delivery System for Drug-Incorporated Nanospheres to Enhance Anti-Tumor Therapeutic Effect

The objective of this study is to construct a platelet-mediated delivery system for drug-incorporated nanospheres. Nanospheres of poly(lactic-co-glycolic acid) (PLGA-NS) with different sizes and surface properties were prepared by changing the preparation parameters, such as the type of polymer surfactant, the concentration of polymer surfactant and PLGA, and the stirring rate. When incubated with platelets, PLGA-NS prepared with poly(vinyl alcohol) suppressed the platelet activation. Scanning electron microscopic and flow cytometry examinations revealed that platelets associated with PLGA-NS (platelet hybrids, PH) had a similar appearance and biological properties to those of the original platelets. In addition, the PH with PLGA-NS specifically adhered onto the substrate pre-coated with fibrin to a significantly great extent compared with PLGA-NS alone. When applied in an in vitro model of tumor tissue which was composed of an upper chamber pre-coated with fibrin and a lower chamber culturing tumor cells, the PH with PLGA-NS incorporating an anti-tumor drug were delivered to the tumor cells through the specific adhesion onto the upper chamber and, consequently, drug release from the upper chamber took place, resulting in the growth suppression of tumor cells. It is concluded that the drug delivery system based on PH is promising for tumor treatment.

Drawing a link between the thromboxane A2 pathway and the role of platelets and tumor cells in ovarian cancer

Ovarian cancer is the most lethal gynecologic malignancy among women. Due to the heterogeneity and complexity of the disease, as well as the insidious onset of symptoms, timely diagnosis remains extremely challenging. Despite recent advances in chemotherapy regimens for ovarian cancer patients, many still suffer from recurrence and ultimately succumb to the disease; thus, there is an urgent need for the identification of novel therapeutic targets. Within this rapidly evolving field, the role of platelets in the ovarian cancer tumor microenvironment has garnered increased attention. It is well-established that platelets and tumor cells exhibit bidirectional communication in which platelets enhance tumor cell invasion, extravasation, and protection from host system defenses, while tumor cells serve as platelet agonists, increasing platelet adhesion, aggregation, and degranulation. This mini-review focuses on the platelet-tumor cell relationship in ovarian cancer, specifically highlighting the essential role of bioactive lipid mediators at this interface.

Effects of Clopidogrel and Proton Pump Inhibitors on Cardiovascular Events in Patients with Type 2 Diabetes Mellitus after Drug-Eluting Stent Implantation: A Nationwide Cohort Study

Objective

To investigate whether there is an increased risk of cardiac events in diabetic patients with a combined therapy of clopidogrel (CLO) and proton pump inhibitors (PPIs) after drug-eluting stent (DES) deployment.

Methods

By using National Health Insurance Research Database, all patients who received CLO with or without PPI therapy within 90 days after undergoing DES (limus-eluting or paclitaxel-eluting stents) deployment were enrolled. Endpoints were acute coronary syndrome (ACS) and readmission for revascularization (percutaneous coronary intervention or coronary artery bypass graft surgery) after 3, 6, and 12 months.

Results

A total of 6,603 diabetic patients received LESs (5,933 in the CLO subgroup and 670 in the CLO plus PPIs subgroup), and 3,202 patients received PESs (2,923 in the CLO subgroup and 279 in the CLO plus PPIs subgroup). The patients who received CLO plus PPIs were at higher risk of ACS than those receiving CLO within 1 year after DES deployment (LESs: 6-month hazard ratio [HR] = 1.63, and 1-year HR = 1.37; PESs: 3-month HR = 1.72). Patients with a history of ACS who received CLO plus PPIs were at higher risk of ACS after LES implantation (HR = 1.55) than those in the CLO group.

Conclusion

In “real-world” diabetic patients with LES deployment, the combination of PPIs and CLO is associated with higher rates of ACS after 6 months and 1 year. Even after correction for confounding factors, concomitant PPI use remained an independent predictor of cardiac events, emphasizing the clinical importance of this drug—drug interaction.

Antiplatelet action of indirubin-3'-monoxime through suppression of glycoprotein VI-mediated signal transduction: a possible role for ERK signaling in platelets

We investigated the antiplatelet activity of indirubin-3'-monoxime (I3O) and the underlying mechanisms. In a rat carotid artery injury model, oral administration (20 mg/kg/day) of I3O for 3 days significantly prolonged occlusion time, and ADP- and collagen-induced platelet aggregation. In washed platelets in vitro, I3O potently inhibited collagen-induced platelet aggregation by suppressing phospholipase Cγ2 (PLCγ2) phosphorylation, subsequently blocking diacylglycerol and arachidonic acid (AA) formation, P-selectin secretion and the production of thromboxane B2. Platelet aggregation induced by phorbol-12-myristate 13-acetate, a protein kinase C (PKC) activator, was inhibited by I3O. Both I3O and U0126, an extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor, markedly reduced collagen-induced phosphorylation of ERK1/2 and p47, resulting in the blockade of cyclooxygenase (COX)-mediated AA metabolite production in AA-treated platelets. I3O suppressed phosphorylation of JNK, p38, GSK-3β, and AKT. I3O inhibited glycoprotein VI (GPVI), as a collagen receptor, by suppressing the phosphorylation of tyrosine kinase Syk of GPVI and the phosphorylation of PLCγ2 and ERK1/2 stimulated by convulxin, as a specific stimulator. Our results indicate that an antiplatelet effect of I3O is due to the suppression of GPVI-mediated signaling pathways. In collagen-stimulated platelets, ERK1/2 phosphorylation is adenylyl cyclase-dependent and leads to the modulation of PKC-p47 signaling and COX-1-mediated AA-metabolic pathways.

Platelets and cancer: a casual or causal relationship: revisited

Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as "First Responders" during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.

Antithrombotic and antiplatelet activities of Soshiho-tang extract

Background

Soshiho-tang (SH; Chinese name, Xiao-Chai-Hu-Tang; Japanese name, Shosaiko-to) is a traditional Korean, Chinese, and Japanese medicine, which has been used to treat various conditions, including hepatitis, liver cirrhosis, and chronic and acute liver disease. SH consists of seven herbal components, of which Scutellaria baicalensis Georgi and Zingiber officinale Roscoe, are reported to have antithrombotic and antiplatelet activities. We investigated the antithrombotic activity of SH, including S. baicalensis and Z. officinale, as an integrative therapy.

Methods

To identify the antithrombotic activity of SH, we used a FeCl₃-induced thrombus formation model. The mechanism of SH-mediated antithrombotic activity was assessed by determining platelet aggregation and coagulation times ex vivo, washed platelet aggregation, serotonin secretion, and thromboxane B₂ formation.

Results

SH prolonged the occlusion time of thrombus formation when applied in a FeCl₃-induced thrombus formation model. SH also inhibited collagen-induced platelet aggregation ex vivo in a concentration-dependent manner; however, it did not affect coagulation. Hence, to identify the antiplatelet effect of SH, we investigated washed platelet aggregations in vitro. SH significantly inhibited various agonist-induced platelet aggregations, and it completely inhibited serotonin secretion and thromboxane B₂ formation.

Conclusions

The findings suggest that SH inhibited FeCl₃-induced thrombus formation through antiplatelet activity, including inhibition of platelet aggregation, and serotonin and TXB₂ production. Thus, SH may be useful as an integrative herbal formula for the treatment of thrombosis.

Interferon-beta induces distinct gene expression response patterns in human monocytes versus T cells

Background

Monocytes, which are key players in innate immunity, are outnumbered by neutrophils and lymphocytes among peripheral white blood cells. The cytokine interferon-β (IFN-β) is widely used as an immunomodulatory drug for multiple sclerosis and its functional pathways in peripheral blood mononuclear cells (PBMCs) have been previously described. The aim of the present study was to identify novel, cell-specific IFN-β functions and pathways in tumor necrosis factor (TNF)-α-activated monocytes that may have been missed in studies using PBMCs.

Methodology/Principal Findings

Whole genome gene expression profiles of human monocytes and T cells were compared following in vitro priming to TNF-α and overnight exposure to IFN-β. Statistical analyses of the gene expression data revealed a cell-type-specific change of 699 transcripts, 667 monocyte-specific transcripts, 21 T cell-specific transcripts and 11 transcripts with either a difference in the response direction or a difference in the magnitude of response. RT-PCR revealed a set of differentially expressed genes (DEGs), exhibiting responses to IFN-β that are modulated by TNF-α in monocytes, such as RIPK2 and CD83, but not in T cells or PBMCs. Known IFN-β promoter response elements, such as ISRE, were enriched in T cell DEGs but not in monocyte DEGs. The overall directionality of the gene expression regulation by IFN-β was different in T cells and monocytes, with up-regulation more prevalent in T cells, and a similar extent of up and down-regulation recorded in monocytes.

Conclusions

By focusing on the response of distinct cell types and by evaluating the combined effects of two cytokines with pro and anti-inflammatory activities, we were able to present two new findings First, new IFN-β response pathways and genes, some of which were monocytes specific; second, a cell-specific modulation of the IFN-β response transcriptome by TNF-α.

JJK694, a synthesized obovatol derivative, inhibits platelet activation by suppressing cyclooxygenase and lipoxygenase activities

Obovatol has various biological activities, including anti-proliferative, neurotrophic, anti-fibrillogenic, anti-platelet, anti-fungal and anti-inflammatory activities. In this study, we investigated the effects of JJK694, a synthesized obovatol derivative, on rabbit platelet activation and its molecular mechanisms. JJK694 significantly inhibited washed rabbit platelet aggregation and serotonin secretion induced by collagen and arachidonic acid, but had little effect on thrombin- or U46619-induced aggregation. These results suggest that JJK694 selectively inhibits collagen- and arachidonic acid-mediated signaling. JJK694 also showed a concentration-dependent decrease in cytosolic Ca(2+) mobilization, but it had no effect on arachidonic acid liberation. On the other hand, it significantly inhibited the formation of arachidonic acid metabolites, including thromboxane A(2) (TXA(2)), prostaglandin D(2), and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), by suppression of cyclooxygenase (COX)-1 and lipoxygenase (LOX) activities. These results indicate that JJK694 hasanti-platelet activities through inhibition of arachidonic acid metabolite production by suppression of COX-1 and LOX activities.

Breast cancer as an acquired thrombophilic state

Cancer is an acquired thrombophilic condition manifested by increased incidence of venous and arterial thromboembolic complications. Despite progress that has been achieved in treatments over the recent years, thromboembolism remains a major complication in patients with breast cancer; it is accompanied by significant morbidity and mortality. Approximately, 1% of breast cancer patients develop venous thromboembolism within 2 years with the highest incidence occurring in the 6 months post diagnosis. Metastatic disease and their comorbidities are the strongest predictors of the development of thrombotic event. The diagnosis of venous thromboembolism is associated with a higher risk of death within 2 years of diagnosis. Thromboembolic events in cancer patients range from abnormal laboratory coagulation tests without specific symptoms to massive thomboembolism and disseminated intravascular coagulation. The underlying pathophysiology is complex and includes the prothrombotic properties of cancer cells, which can be enhanced by anticancer treatment modalities, such as surgery, hormonal agents, and chemotherapy. Primary thromboprophylaxis in cancer patients should be individualized according to risk. For secondary prevention, several clinical studies have shown that low molecular weight heparin has improved patients' compliance, cancer outcomes and overall survival. This review summarizes the available data on the pathogenesis and clinical approach of hemostatic changes in breast cancer.