Promyelocytic extracellular chromatin exacerbates coagulation and fibrinolysis in acute promyelocytic leukemia

Hemorrhage in acute promyelocytic leukemia-fibrinolysis in focus

Coagulopathy continues to be a major challenge in the management of patients with acute promyelocytic leukemia (APL). Novel differentiating agents have led to improved survival in these patients, but perturbations in coagulation continue to have an impact on their prognosis. The most worrisome of coagulation disturbances is bleeding, which is not an uncommon cause of early death in APL. Despite this, there are no consistent predictors of this high risk of fatal hemorrhage in APL. In this context, the fibrinolytic system has been identified as a crucial role player in APL coagulopathy. However, the current guidelines for the management of APL give little regard to tests that measure the fibrinolytic system while giving more importance to close monitoring of conventional coagulation tests and platelet counts to identify the coagulopathy. More recently, viscoelastic tests have come to usefulness in determining global hemostasis and have been widely used for "diagnosing" hyperfibrinolysis in selected clinical settings. In this review, we attempt to describe risk assessment models for diagnosing APL coagulopathy, describe the possible application of viscoelastic tests in this setting, and persuade clinicians to reconsider the use of antifibrinolytics to improve survival of APL patients.

Targeting neutrophil extracellular traps: A novel strategy in hematologic malignancies

Neutrophil extracellular traps (NETs) have emerged as a critical factor in malignant hematologic disease pathogenesis. These structures, comprising DNA, histones, and cytoplasmic proteins, were initially recognized for their role in immune defense against microbial threats. Growing evidence suggests that NETs contribute to malignant cell progression and dissemination, representing a double-edged sword. However, there is a paucity of reports on its involvement in hematological disorders. A comprehensive understanding of the intricate relationship between malignant cells and NETs is necessary to explore effective therapeutic strategies. This review highlights NET formation and mechanisms underlying disease pathogenesis. Moreover, we discuss recent advancements in targeted inhibitor development for selective NET disruption, empowering precise design and efficacious therapeutic interventions for malignant hematologic diseases.

Damage to endothelial barriers and its contribution to long COVID

The world continues to contend with COVID-19, fueled by the emergence of viral variants. At the same time, a subset of convalescent individuals continues to experience persistent and prolonged sequelae, known as long COVID. Clinical, autopsy, animal and in vitro studies all reveal endothelial injury in acute COVID-19 and convalescent patients. Endothelial dysfunction is now recognized as a central factor in COVID-19 progression and long COVID development. Different organs contain different types of endothelia, each with specific features, forming different endothelial barriers and executing different physiological functions. Endothelial injury results in contraction of cell margins (increased permeability), shedding of glycocalyx, extension of phosphatidylserine-rich filopods, and barrier damage. During acute SARS-CoV-2 infection, damaged endothelial cells promote diffuse microthrombi and destroy the endothelial (including blood-air, blood-brain, glomerular filtration and intestinal-blood) barriers, leading to multiple organ dysfunction. During the convalescence period, a subset of patients is unable to fully recover due to persistent endothelial dysfunction, contributing to long COVID. There is still an important knowledge gap between endothelial barrier damage in different organs and COVID-19 sequelae. In this article, we mainly focus on these endothelial barriers and their contribution to long COVID.

Impaired fibrinolysis and increased clot strength are potential risk factors for thrombosis in lymphoma

Thrombosis and bleeding are significant contributors to morbidity and mortality in patients with hematological cancer, and the impact of altered fibrinolysis on bleeding and thrombosis risk is poorly understood. In this prospective cohort study, we investigated the dynamics of fibrinolysis in patients with hematological cancer. Fibrinolysis was investigated before treatment and 3 months after treatment initiation. A dynamic clot formation and lysis assay was performed beyond the measurement of plasminogen activator inhibitor 1, tissue- and urokinase-type plasminogen activators (tPA and uPA), plasmin-antiplasmin complexes (PAP), α-2-antiplasmin activity, and plasminogen activity. Clot initiation, clot propagation, and clot strength were assessed using rotational thromboelastometry. A total of 79 patients were enrolled. Patients with lymphoma displayed impaired fibrinolysis with prolonged 50% clot lysis time compared with healthy controls (P = .048). They also displayed decreased clot strength at follow-up compared with at diagnosis (P = .001). A patient with amyloid light-chain amyloidosis having overt bleeding at diagnosis displayed hyperfibrinolysis, indicated by a reduced 50% clot lysis time, α-2-antiplasmin activity, and plasminogen activity, and elevated tPA and uPA. A patient with acute promyelocytic leukemia also displayed marked hyperfibrinolysis with very high PAP, indicating extreme plasmin generation, and clot formation was not measurable, probably because of the extremely fast fibrinolysis. Fibrinolysis returned to normal after treatment in both patients. In conclusion, patients with lymphoma showed signs of impaired fibrinolysis and increased clot strength, whereas hyperfibrinolysis was seen in patients with acute promyelocytic leukemia and light-chain amyloidosis. Thus, investigating fibrinolysis in patients with hematological cancer could have diagnostic value.

Cerebral venous thrombosis in patients with autoimmune disease, hematonosis or coronavirus disease 2019: Many familiar faces and some strangers

BACKGROUND

Cerebral venous thrombosis, a rare stroke, is characterized by neurological dysfunction caused by bleeding and/or infarction resulting from venous sinus thrombosis, the so-called venous stroke. Current guidelines recommend anticoagulants as first-line therapy in the treatment of venous stroke. With complicated causes of cerebral venous thrombosis, treatment is difficult, especially when combined with autoimmune diseases, blood diseases, and even COVID-19.

AIMS

This review summarizes the pathophysiological mechanisms, epidemiology, diagnosis, treatment, and clinical prognosis of cerebral venous thrombosis combined with autoimmune diseases, blood diseases, or infectious diseases such as COVID-19.

CONCLUSION

A systematic understanding of particular risk factors that should not be neglected when unconventional cerebral venous thrombosis occurs and for a scientific understanding of pathophysiological mechanisms, clinical diagnosis, and treatment, thus contributing to knowledge on special types of venous stroke.

Combined FOLFOX4 with all-trans retinoic acid versus FOLFOX4 with placebo in treatment of advanced hepatocellular carcinoma with extrahepatic metastasis: a randomized, double-blind comparative study

The majority of hepatocellular carcinoma (HCC) cases are diagnosed at an advanced stage. Currently, there are only a few therapeutic methods available for patients with advanced HCC and extrahepatic metastasis (EHM). Systemic chemotherapy, such as FOLFOX4 (infusions of fluorouracil, leucovorin, and oxaliplatin), has been reported for treating advanced HCC with EHM, but its effectiveness is very poor. In this randomized, double-blind, placebo-controlled study, we aimed to assess the efficacy and safety of FOLFOX4 with all-trans-retinoic acid (ATRA) as a palliative treatment for HCC patients with EHM, compared to FOLFOX4 with a placebo. The primary endpoint was overall survival (OS), and subsequently, an exploratory model was developed based on bioinformatics to predict the efficacy of FOLFOX4-ATRA treatment. A total of 108 patients were randomly assigned in a 1:1 ratio to receive either FOLFOX4-ATRA or FOLFOX4-placebo. The intention-to-treat (ITT) population showed a median OS of 16.2 months for the FOLFOX4-ATRA group, compared with 10.7 months for the FOLFOX4-placebo group (HR 0.56, 95% CI 0.33-0.93; p = 0.025). The median progression-free survival (PFS) was 7.1 months for the FOLFOX4-ATRA group and 4.2 months for the FOLFOX4-placebo group (HR 0.62, 95% CI 0.41-0.94; p = 0.024). A panel of proteins with unique upregulation during complete response (CR) (SOD3, TTR, SSC5D, GP5, IGKV1D-33) and partial response (PR) (TGFB1, GSS, IGHV5-10-1) effectively predicted CR and PR in patients treated with FOLFOX4-ATRA, as compared to FOLFOX4-placebo. The results suggest that FOLFOX4-ATRA is a safe and effective treatment for patients with advanced HCC and EHM in eastern China.

Overexpression of CASP1 triggers acute promyelocytic leukemia cell pyroptosis and differentiation

Caspase-1 (CASP1)-mediated classical pyroptosis plays a key role in cancer development and management, however, the role of CASP1 and its regulation has not yet been documented for acute promyelocytic leukemia (APL). Here, we found that CASP1/GSDMD had lower expression in patients with APL and most other subtypes of primary de novo acute myeloid leukemia (AML) and was increased in all-trans-retinoic acid (ATRA)-treated APL cells. We showed that ATRA increases and activates CASP1 to trigger the pyroptosis and differentiation of APL cells. Mechanistically, ATRA could induce CASP1 expression via the IFNγ/STAT1 pathway in APL cells. In conclusion, ATRA-induced activation of CASP1 may serve as a suppressor in APL progression, as it triggers pyroptotic cell death and differentiation.

Microparticle Phosphatidylserine Mediates Coagulation: Involvement in Tumor Progression and Metastasis

Tumor progression and cancer metastasis has been linked to the release of microparticles (MPs), which are shed upon cell activation or apoptosis and display parental cell antigens, phospholipids such as phosphatidylserine (PS), and nucleic acids on their external surfaces. In this review, we highlight the biogenesis of MPs as well as the pathophysiological processes of PS externalization and its involvement in coagulation activation. We review the available evidence, suggesting that coagulation factors (mainly tissue factor, thrombin, and fibrin) assist in multiple steps of tumor dissemination, including epithelial-mesenchymal transition, extracellular matrix remodeling, immune escape, and tumor angiogenesis to support the formation of the pre-metastatic niche. Platelets are not just bystander cells in circulation but are functional players in primary tumor growth and metastasis. Tumor-induced platelet aggregation protects circulating tumor cells (CTCs) from the blood flow shear forces and immune cell attack while also promoting the binding of CTCs to endothelial cells and extravasation, which activates tumor invasion and sustains metastasis. Finally, in terms of therapy, lactadherin can inhibit coagulation by competing effectively with coagulation factors for PS binding sites and may similarly delay tumor progression. Furthermore, we also investigate the therapeutic potential of coagulation factor inhibitors within the context of cancer treatment. The development of multiple therapies targeting platelet activation and platelet-tumor cell interactions may not only reduce the lethal consequences of thrombosis but also impede tumor growth and spread.

Neutrophil extracellular traps contribute to coagulopathy after traumatic brain injury

Coagulopathy contributes to the majority of deaths and disabilities associated with traumatic brain injury (TBI). Whether neutrophil extracellular traps (NETs) contribute to an abnormal coagulation state in the acute phase of TBI remains unknown. Our objectives were to demonstrate the definitive role of NETs in coagulopathy in TBI. We detected NET markers in 128 TBI patients and 34 healthy individuals. Neutrophil-platelet aggregates were detected in blood samples from TBI patients and healthy individuals using flow cytometry and staining for CD41 and CD66b. Endothelial cells were incubated with isolated NETs and we detected the expression of vascular endothelial cadherin, syndecan-1, thrombomodulin, von Willebrand factor, phosphatidylserine, and tissue factor. In addition, we established a TBI mouse model to determine the potential role of NETs in TBI-associated coagulopathy. NET generation was mediated by high mobility group box 1 (HMGB1) from activated platelets and contributed to procoagulant activity in TBI. Furthermore, coculture experiments indicated that NETs damaged the endothelial barrier and caused these cells to assume a procoagulant phenotype. Moreover, the administration of DNase I before or after brain trauma markedly reduced coagulopathy and improved the survival and clinical outcome of mice with TBI.

ATRA treatment slowed P-selectin-mediated rolling of flowing HL60 cells in a mechano-chemical-dependent manner

All-trans retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) toward granulocytes may trigger APL differentiation syndrome (DS), but there is less knowledge about the mechano-chemical regulation mechanism of APL DS under the mechano-microenvironment. We found that ATRA-induced changes in proliferation, morphology, and adhesive molecule expression levels were either dose or stimulus time dependent. An optimal ATRA stimulus condition for differentiating HL60 cells toward neutrophils consisted of 1 × 10^-6 M dose and 120 h of stimulus time. Under wall shear stresses, catch-slip bond transition governs P-selectin-mediated rolling for neutrophils and untreated or ATRA-treated (1 × 10^-6 M, 120 h) HL60 cells. The ATRA stimuli slowed down the rolling of HL60 cells on immobilized P-selectin no matter whether ICAM-1 was engaged. The β2 integrin near the PSGL-1/P-selectin axis would be activated within sub-seconds for each cell group mentioned above, thus contributing to slow rolling. A faster β2 integrin activation rate and the higher expression levels of PSGL-1 and LFA-1 were assigned to induce the over-enhancement of ATRA-treated HL60 adhesion in flow, causing APL DS development. These findings provided an insight into the mechanical-chemical regulation for APL DS development via ATRA treatment of leukemia and a novel therapeutic strategy for APL DS through targeting the relevant adhesion molecules.

Inflammatory cytokines induce neutrophil extracellular traps interaction with activated platelets and endothelial cells exacerbate coagulation in moderate and severe essential hypertension

BACKGROUND

Essential hypertension (EH) patients suffer from paradoxically thrombotic rather than haemorrhagic, although the exact mechanism remains elusive. Our aim is to explore whether and how neutrophil extracellular traps (NETs) play the procoagulant role in EH patients, as well as evaluated whether the NET releasing were triggered by inflammatory cytokines.

METHODS

The concentration of plasma NETs components were detected by ELISA. The morphology of cells and NETs formation were analysed using immunofluorescence. Procoagulant activity was analysed by clotting time, purified coagulation complex and fibrin generation assays. Phosphatidylserine (PS) exposure on endothelial cells (ECs) was analysed with flow cytometry.

RESULTS

Moderate to severe EH patients plasma NETs levels were significantly higher compared to mild EH patients or controls. Furthermore, inflammatory cytokines can induce NETs generation, depleting these patients plasma inflammatory cytokines led to a reduction in NET releasing. NETs from moderate to severe EH patients neutrophils led to significantly decreased clotting time (CT), increased potency to generate thrombin and fibrin (all P  < 0.05). These procoagulant effects were markedly attenuated by approximately 70% using DNase I. Additionally, high concentrations NETs exerted a strong cytotoxic effect on ECs, conferring them a procoagulant phenotype.

CONCLUSION

Our study reveals that EH drives a systemic inflammatory environment, which, in turn, drives neutrophils to prime and NET releasing, and found a link between hypercoagulability and NETs levels in moderate to severe EH patients. Therefore, anti-inflammatory combined with block the generation of NETs may represent a new therapeutic target for preventing thrombosis in EH patients.

Neutrophil extracellular traps: New players in cancer research

NETs are chromatin-derived webs extruded from neutrophils as a result of either infection or sterile stimulation using chemicals, cytokines, or microbes. In addition to the classical role that NETs play in innate immunity against infection and injuries, NETs have been implicated extensively in cancer progression, metastatic dissemination, and therapy resistance. The purpose of this review is to describe recent investigations into NETs and the roles they play in tumor biology and to explore their potential as therapeutic targets in cancer treatment.

The cross-talk of lung and heart complications in COVID-19: Endothelial cells dysfunction, thrombosis, and treatment

The pandemic respiratory illness SARS-CoV-2 has increasingly been shown to be a systemic disease that can also have profound impacts on the cardiovascular system. Although associated cardiopulmonary sequelae can persist after infection, the link between viral infection and these complications remains unclear. There is now a recognized link between endothelial cell dysfunction and thrombosis. Its role in stimulating platelet activation and thrombotic inflammation has been widely reported. However, the procoagulant role of microparticles (MPs) in COVID-19 seems to have been neglected. As membrane vesicles released after cell injury or apoptosis, MPs exert procoagulant activity mainly by exposing phosphatidylserine (PS) on their lipid membranes. It can provide a catalytic surface for the assembly of the prothrombinase complex. Therefore, inhibiting PS externalization is a potential therapeutic strategy. In this paper, we describe the pathophysiological mechanism by which SARS-CoV-2 induces lung and heart complications through injury of endothelial cells, emphasizing the procoagulant effect of MPs and PS, and demonstrate the importance of early antithrombotic therapy. In addition, we will detail the mechanisms underlying hypoxia, another serious pulmonary complication related to SARS-CoV-2-induced endothelial cells injury and discuss the use of oxygen therapy. In the case of SARS-CoV-2 infection, virus invades endothelial cells through direct infection, hypoxia, imbalance of the RAAS, and cytokine storm. These factors cause endothelial cells to release MPs, form MPs storm, and eventually lead to thrombosis. This, in turn, accelerates hypoxia and cytokine storms, forming a positive feedback loop. Given the important role of thrombosis in the disease, early antithrombotic therapy is an important tool for COVID-19. It may maintain normal blood circulation, accelerating the clearance of viruses, waning the formation of MPs storm, and avoiding disease progression.

CD44-fibrinogen binding promotes bleeding in acute promyelocytic leukemia by in situ fibrin(ogen) deposition

Early haemorrhagic death is still the main obstacle for the successful treatment of acute promyelocytic leukaemia (APL). However, the mechanisms underlying haemostatic perturbations in APL have not been fully elucidated. Here, we report that CD44 on the membrane of APL blasts and NB4 cells ligated bound fibrinogen, resulting in in situ deposition of fibrin and abnormal fibrin distribution. Clots formed by leukaemic cells in response to CD44 and fibrinogen interaction exhibited low permeability and resistance to fibrinolysis. Using flow cytometry and confocal microscopy, we found that CD44 was also involved in platelet and leukaemic cell adhesion. CD44 bound activated platelets but not resting platelets through interaction with P-selectin. APL cell-coated fibrinogen-activated platelets directly induce enhanced procoagulant activity of platelets. In vivo studies revealed that CD44 knockdown shortened bleeding time, increased the level of fibrinogen, and elevated the number of platelets by approximately 2-fold in an APL mouse model. Moreover, CD44 expression on leukaemic cells in an APL mouse model was not only associated with bleeding complications but was also related to the wound healing process and the survival time of APL mice. Collectively, our results suggest that CD44 may be a potential intervention target for preventing bleeding complications in APL.

Persistent Lung Injury and Prothrombotic State in Long COVID

Lung injury may persist during the recovery period of COVID-19 as shown through imaging, six-minute walk, and lung function tests. The pathophysiological mechanisms leading to long COVID have not been adequately explained. Our aim is to investigate the basis of pulmonary susceptibility during sequelae and the possibility that prothrombotic states may influence long-term pulmonary symptoms of COVID-19. The patient’s lungs remain vulnerable during the recovery stage due to persistent shedding of the virus, the inflammatory environment, the prothrombotic state, and injury and subsequent repair of the blood-air barrier. The transformation of inflammation to proliferation and fibrosis, hypoxia-involved vascular remodeling, vascular endothelial cell damage, phosphatidylserine-involved hypercoagulability, and continuous changes in serological markers all contribute to post-discharge lung injury. Considering the important role of microthrombus and arteriovenous thrombus in the process of pulmonary functional lesions to organic lesions, we further study the possibility that prothrombotic states, including pulmonary vascular endothelial cell activation and hypercoagulability, may affect long-term pulmonary symptoms in long COVID. Early use of combined anticoagulant and antiplatelet therapy is a promising approach to reduce the incidence of pulmonary sequelae. Essentially, early treatment can block the occurrence of thrombotic events. Because impeded pulmonary circulation causes large pressure imbalances over the alveolar membrane leading to the infiltration of plasma into the alveolar cavity, inhibition of thrombotic events can prevent pulmonary hypertension, formation of lung hyaline membranes, and lung consolidation.

Extracellular Traps Increase Burden of Bleeding by Damaging Endothelial Cell in Acute Promyelocytic Leukaemia

The rate of complete remission of acute promyelocytic leukemia (APL) is currently over 90% because of the use of all-trans retinoic acid (ATRA) with arsenic trioxide (ATO). However, hemorrhagic mortality has emerged as the most significant barrier to APL-induced remission. Neutrophils extracellular traps (NETs/ETs) cause vascular leakage by damaging the integrity of endothelial cells. We have previously demonstrated that APL cells treated with ATRA/ATO undergo a cell death process, releasing extracellular chromatin, termed ETosis/NETosis. However, the mechanism underlying the involvement of ETs in endothelial injury in APL remain largely unknown. Here, we analysed the ability of mature and immature neutrophils to release ETs, and their interaction with platelets (PLTs) in APL. Importantly, the effect of ETs on vascular endothelium in APL was discussed. Our results showed that the ability of immature neutrophils to release ETs was impaired in APL, whereas mature neutrophils produced ETs, which were associated with activated PLTs. Moreover, ATRA+ATO induced immature neutrophil differentiation, as well as increased the release of ETs from mature neutrophils. The excessive ETs damaged endothelial cells, causing blood cell leakage. Removing ETs using DNase 1 alleviated endothelial damage and improved blood cells leakage. Our results indicate that vascular endothelial injury is at least partially associated with ETs in APL, and that targeting ETs production may be an effective approach for relieving vascular leakage and reducing the burden of bleeding in APL.

Intracranial Hemorrhage Secondary to Newly Diagnosed Acute Promyelocytic Leukemia: A Cautionary Tale

Acute promyelocytic leukemia (APL) typically presents with complications from pancytopenia, generalized weakness, and hemorrhagic findings, with a distinguishing feature being the associated predilection of disseminated intravascular coagulation (DIC). APL is characterized by the halting of cellular differentiation in the promyelocyte stage, and balanced chromosomal translocation t(15;17) (q24;q21) that forms the promyelocytic leukemia-retinoic acid receptor-α (PML-RARA) fusion protein present in 95% of cases. APL has a high rate of early mortality secondary to coagulopathy, lending to the imperative need to begin a differentiation agent as soon as the disease is suspected, with all-trans retinoic acid (ATRA) being the most common differentiation agent. Herein, we present the case of a 32-year-old man presenting with non-specific symptoms of fatigue and scattered bruising, who was found to have an intracranial hemorrhage (ICH) in the setting of suspected APL. This case illuminates the importance of early brain imaging in suspected cases of APL to conceivably lessen the severity of hemorrhagic complications and represents a cautionary tale for similar cases in the future.

Acute promyelocytic leukemia presenting as recurrent venous and arterial thrombotic events: a case report and review of the literature

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia characterized by a translocation of chromosomes 15 and 17, creating an alternation in the retinoic acid receptor-alpha (RAR-alpha) gene. This leads to excessive medullary production of promyelocytic blasts, which are frequently associated with the hemorrhagic complications seen in APL. In contrast, APL-associated thrombosis occurs much less frequently and is an underappreciated life-threatening manifestation of the disease. Most thrombotic events occur during induction chemotherapy with all-transretinoic acid and are rarely seen as the initial presentation on APL. Here we report an exceedingly rare case of a patient with recurrent venous and arterial thrombotic events, including deep vein thrombosis, bilateral segmental pulmonary embolism, an ischemic stroke, splenic infarcts, and renal infarcts, later found to have APL. We aim to discuss the most recent understanding of the pathogenesis of APL-associated thrombosis and to summarize the literature of this rare presentation of APL.

Neurologic complications of acute myeloid leukemia. Diagnostic approach and therapeutic modalities

Acute myeloid leukemia (AML) comprises a heterogeneous group of aggressive blood malignancies that arise from clonal expansion of malignant hematopoietic precursor cells in the bone marrow. Neurologic manifestations of these malignancies are manifolds. AML is the most common form of acute leukemia in adults and this review describes the neurologic complications in this age group. Neurologic symptoms and signs may develop in AML either from a direct neoplastic involvement of the central or the peripheral nervous system or as an indirect effect of the disease process. Direct involvement of the nervous system includes invasion of the central or the peripheral nervous system (parenchymal and leptomeningeal dissemination, myeloid sarcoma, neuroleukemiosis). Thrombotic and hemorrhagic events are common manifestations of indirect involvement of the nervous system and they are the outcome of hyperleukocytosis, thrombocytopenia and coagulopathy. Many neurologic complications are iatrogenic and include diverse categories such as lumbar puncture and intrathecal or systemic chemotherapy and targeted therapies, radiotherapy and allogeneic stem cell transplantation. Most neurologic manifestations require urgent treatment and confer a poor prognosis. This review describes the neurologic complications of acute myeloid malignancies in the era of contemporary treatment. Those manifestations require expert consideration of their origin as they are being identified with increasing frequency as patients survive longer.

Advances in the management of coagulopathy in acute promyelocytic leukemia

Since the introduction of all-trans retinoic acid and, more recently, arsenic trioxide into the therapy of acute promyelocytic leukemia (APL), significant improvements in patient outcomes have been achieved, and this disease has become the most curable subtype of acute myeloid leukemia. However, while primary leukemia resistance has virtually disappeared, a sizable fraction of APL patients still die before or during induction therapy. Hemorrhagic death still remains the major problem during this early phase of treatment and, to a lesser extent, deaths due to infection, differentiation syndrome and other causes. Patients with APL typically present with a range of laboratory abnormalities consistent with the diagnosis of disseminated intravascular coagulation and hyperfibrinolysis. This APL-associated coagulopathy, as a result of a dysregulation of the hemostatic system due to the imbalance between procoagulant, anticoagulant and profibrinolytic mechanisms, may show a variety of clinical manifestations, ranging from minimal bleeding or localized thrombosis to lethal or life-threatening hemorrhages or thrombotic events that sometimes occur concomitantly. Hemorrhagic events are the most common cause of death associated with APL coagulopathy, but thrombosis, a less recognized and probably underestimated life-threatening manifestation of the thrombo-hemorrhagic syndrome, is also a non-negligible cause of morbidity and mortality in patients with APL. In this article, we aim to discuss recent advances in the knowledge of pathogenesis, predictors of thrombo-hemorrhagic events, management of coagulopathy associated with APL and the controversial issues that still persist.

Tissue factor-bearing microparticles are a link between acute promyelocytic leukemia cells and coagulation activation: a human subject study

Acute promyelocytic leukemia (APL) cells constitutively express a large amount of tissue factor (TF) antigen, most of which is present in the cytoplasm. Coagulopathy may persist after induction therapy. We evaluated the overall role of circulating microparticles (MPs) in coagulation activation in APL-associated coagulopathy before and during induction therapy. Eleven adult patients with ≥ World Health Organization's (WHO) grade 2 bleeding events and 11 sex- and age-matched healthy controls were selected. All patients received arsenic trioxide alone as induction therapy. MP-associated TF (MP-TF) activity and MP procoagulant activity (MP-PCA) and 12 coagulation- and anticoagulation-associated indexes were measured before, during, and after induction therapy. Correlation between MP-associated indexes and the other 12 indexes was analyzed in patients. The MP-TF activity was negligible in controls, whereas it markedly increased in patients, dropped rapidly after treatment, and returned to normal at the end of induction therapy. The MP-PCA was similar between patients and controls. The correlation analysis revealed that TF-bearing MPs in patients mainly originated from APL cells. Partially differentiated APL cells could also release TF-bearing MPs, and the higher the degree of APL cell differentiation, the lower the ability of APL cells to release TF-bearing MPs. MP-TF was the main source of active TF in plasma and an important contributor for the coagulation activation in APL-associated coagulopathy. It was MPs released by APL cells/partially differentiated APL cells that served as the vehicle to transfer the large amount of TF to plasma to activate coagulation.

Management of Disseminated Intravascular Coagulation in Acute Leukemias

Disseminated intravascular coagulation (DIC) is characterized by the intravascular activation of coagulation with loss of localization arising from different causes, and is diagnosed using scoring systems which rely upon the presence of an underlying disorder compatible with DIC alongside hemostatic derangements such as low platelet count, prolonged prothrombin time, and elevated fibrinogen degradation products. DIC is common in patients with acute leukemia, with prevalence ranging from 17 to 100% in acute promyelocytic leukemia (APL) and 8.5 to 25% in acute lymphoblastic leukemia (ALL) and non-APL acute myeloid leukemia (AML). The pathophysiology is complex and varies between the leukemia subtypes, and is not fully reflected by the laboratory markers currently used to classify DIC. Similarly, the clinical consequence of DIC in acute leukemia also varies across the types of leukemia. DIC is primarily associated with bleeding in APL, while thrombosis is the dominant phenotype in ALL and non-APL AML. The cornerstone of managing DIC is the treatment of the underlying disease, as exemplified by the important role of early administration of all-trans retinoic acid in APL. Other aspects of management focus on supportive care aimed at minimizing the risk of bleeding, via transfusion of blood products. The use of blood products is more liberal in APL, due to the hemorrhagic phenotype and unacceptably high rates of early hemorrhagic death. This review will focus on the pathophysiology, risk factors, clinical implications, and the management of DIC in patients across the spectrum of acute leukemias.

Neutrophil extracellular traps exacerbate coagulation and endothelial damage in patients with essential hypertension and hyperhomocysteinemia

Patients with essential hypertension (EH) and hyperhomocysteinemia (HHCY) suffer from more increased thrombotic events than those in EH alone. However, the underlying mechanisms for this effect are not well understood. This study hypothesized that neutrophil extracellular trap (NET) releasing may be triggered by HHCY in patients in EH, thereby predisposing them to a more hypercoagulable state. Using a modified-capture enzyme-linked immunosorbent assay (ELISA) method, we observed that cell-free DNA (CF-DNA) and myeloperoxidase DNA (MPO-DNA) in patients With EH and HHCY were significantly higher. The NET formation was also positively correlated with homocysteine levels, neutrophil-lymphocyte ratio (NLR), and hypercoagulable markers (thrombin-antithrombin complex, D-dimers). Furthermore, neutrophils from patients in EH with HHCY were found to be predisposed to amplified NET release when compared to patients in EH without HHCY or CTR. Coagulation function assays showed that NETs in patients With EH and HHCY resulted in a significantly increased ability to generate thrombin and fibrin than in those in EH without HHCY or CTR. These procoagulant effects of NETs in patients With EH and HHCY were markedly inhibited (approximately 70%) by the cleavage of NETs with DNase I. Isolated NETs from patients With EH and HHCY neutrophils also exerted a strong cytotoxic effect on endothelial cells (ECs), converted them to apoptosis. This study revealed a previously unrecognized association between the hypercoagulable state and neutrophils in patients With EH and HHCY. Therefore, blocking NETs may represent a new therapeutic objective for preventing thrombosis in these patients.

Endothelial damage and a thin intercellular fibrin network promote haemorrhage in acute promyelocytic leukaemia

Background

The role of vascular endothelium in acute promyelocytic leukaemia (APL) remains unknown. We aimed to investigate the mechanisms by which APL cells interact with endothelial cells (ECs) and to further explore how the endothelium affects bleeding as well as therapeutic interventions.

Method

APL cells and an original APL cell line, NB4 cells, were used for experiments. The effects of leukaemic cells on ECs were analyzed in vitro and in vivo. Moreover, the endothelial barrier function and procoagulant activity were detected. An APL mouse model was established for in vivo studies.

Findings

APL cells interacted with ECs via ICAM-1 and VCAM-1 receptors to disrupt endothelial integrity. This binding activated MLCK signaling, resulting in the trans-endothelial passage of protein and red blood cells (RBCs). Combined treatment with asiatic acid or anti-adhesion receptor antibody inhibited the response of ECs to APL cells, thereby preventing APL-associated haemorrhage in vitro and in vivo. Activated ECs exhibited a procoagulant phenotype after phosphatidylserine exposure. Plasma from APL patients formed a thin fibrin network between procoagulant ECs, and this intercellular fibrin decreased the passage of albumin and RBCs. Ex vivo addition of fibrinogen further enhanced this barrier function in a dose-dependent manner.

Interpretation

Endothelial damage induced by leukaemic cell adherence promotes haemorrhaging in APL. Stabilization of ECs, decreasing adhesion receptor expression, and increasing fibrinogen transfusion levels may be a new therapeutic avenue to alleviate this fatal bleeding complication.

Funding

National Science Foundation of China (81670128, 81873433).

Effect of daunorubicin on acute promyelocytic leukemia cells using nuclear magnetic resonance spectroscopy-based metabolomics

The aim of this study was to determine several key metabolites as potential biomarkers of daunorubicin (DNR) treatment of acute promyelocytic leukemia (APL) using APL blasts and NB4 cells. Samples which were obtained from 16 newly diagnosed APL patients and human APL NB4 cell lines were exposed to increasing concentrations of DNR (0 μM, 0.1 μM, 0.5 μM and 1.0 μM). Electron microscopy and Nuclear Magnetic Resonance (NMR) spectroscopy confirmed that there were clear differences between controls and DNR-treated groups, with the resultant models having excellent predictive and discriminative abilities. Four metabolites meeting the biomarker requirements were identified. KEGG analyses revealed that these biomarkers were associated with the metabolism of fat, choline, and glucose. These findings offered vital information about the effects of chemotherapies on the whole body biochemistry which might be important for monitoring apoptosis and injury to cells in order to reduce chemotherapies-induced side effects.

Hemorrhage in acute promyelocytic leukemia: Can it be predicted and prevented?

Hemorrhagic death is the leading cause of treatment failure in acute promyelocytic leukemia (APL). Our ability to identify patients at greatest risk of hemorrhage, and to actively prevent hemorrhage, remains limited. Nevertheless, some data is available to guide contemporary clinical practice and future investigation. Circulating disease burden, best represented by the peripheral WBC / blast count, is the most consistent predictor of major and fatal bleeding risk. In contrast, laboratory markers of disseminated intravascular coagulation (DIC) appear to be poor predictors. A number of interventions have been posited to reduce bleeding risk. Prompt initiation of all-trans retinoic acid (ATRA), avoidance of invasive procedures, transfusion support, and cytoreduction all have theoretical merit. Though they lack strong evidence to support their benefit with respect to bleeding, they are associated with limited risks, and are therefore advisable. Low-dose therapeutic heparin and antifibrinolytics have not shown the ability to positively modify bleeding risk, and heparin has been associated with harm. Thrombomodulin has shown promise in limited retrospective studies however further prospective data are needed. rFVIIa may have a role in cases of life-threatening bleeding however evidence is largely anecdotal. Additional studies evaluating the above interventions, and investigating other potential interventions are needed.

Blood Parameters in Treatment with Arsenic Trioxide in Acute Promyelocytic Leukemia: A Systematic Review

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML). APL is famed with some special blood coagulation disorders such as disseminated intravascular coagulation (DIC). The therapeutic methods of APL contain All Trans Retinoic Acid (ATRA), arsenic trioxide (ATO) or/and chemotherapy. Many studies have been done on APL blood disorders and its treatment. These studies have shown different results. In this systematic article, we tried to review the effect of ATO therapy with or without ATRA and chemotherapy on DIC parameters (D-dimer, Prothrombin Time, Activated Partial Thrombin Time, Platelet count) in APL patients. The result of included studies demonstrated that although ATO can reduce the number of malignant cells in the bone marrow and peripheral blood, it does not have enough potential to attenuate the danger of high score DIC that is usual in APL patients and should be better to be used with other therapeutic methods.

Bacterial Endotoxin Activates the Coagulation Cascade through Gasdermin D-Dependent Phosphatidylserine Exposure

Excessive activation of the coagulation system leads to life-threatening disseminated intravascular coagulation (DIC). Here, we examined the mechanisms underlying the activation of coagulation by lipopolysaccharide (LPS), the major cell-wall component of Gram-negative bacteria. We found that caspase-11, a cytosolic LPS receptor, activated the coagulation cascade. Caspase-11 enhanced the activation of tissue factor (TF), an initiator of coagulation, through triggering the formation of gasdermin D (GSDMD) pores and subsequent phosphatidylserine exposure, in a manner independent of cell death. GSDMD pores mediated calcium influx, which induced phosphatidylserine exposure through transmembrane protein 16F, a calcium-dependent phospholipid scramblase. Deletion of Casp11, ablation of Gsdmd, or neutralization of phosphatidylserine or TF prevented LPS-induced DIC. In septic patients, plasma concentrations of interleukin (IL)-1α and IL-1β, biomarkers of GSDMD activation, correlated with phosphatidylserine exposure in peripheral leukocytes and DIC scores. Our findings mechanistically link immune recognition of LPS to coagulation, with implications for the treatment of DIC.

Neutrophil extracellular traps enhance procoagulant activity in patients with oral squamous cell carcinoma

BACKGROUND

Hypercoagulability is a major cancer-associated complication linked to poor patient prognosis. The production of neutrophil extracellular traps (NETs) is increasingly found to be linked with the development and metastasis of cancer, as well as with thrombi formation in cancer patients. We hypothesized that the neutrophil NET release may be triggered by specific cytokines in oral squamous cell carcinoma (OSCC) patients, thereby predisposing them to a hypercoagulable state. Moreover, we have evaluated the interaction between NETs and endothelial cells (ECs).

METHODS

NET procoagulant activity was assessed based on fibrin and purified coagulation complex production assays, as well as by measuring coagulation time (CT). We further used confocal microscopy to quantify the exposure of phosphatidylserine (PS), fibrin strands, and cell FVa/Xa binding.

RESULTS

OSCC patients with stage III/IV exhibited elevated plasma NET levels compared to stage I/II or CTR (all P < 0.05). Neutrophils from OSCC patients are predisposed to amplified NET release compared to those from CTR. Furthermore, depleting IL-8, IL-6, and TNF-α led to a reduction in NET release in the plasma. OSCC NETs increased thrombin and fibrin generation and decreased CT significantly (P < 0.05). When NETs were isolated and used to treat ECs, these cells exhibited disrupted morphology by retracting from their cell-cell junctions and convert to a procoagulant phenotype. These effects could be attenuated by approximately 70% using DNase I.

CONCLUSIONS

Our findings are consistent with a model wherein OSCC drives a systemic inflammatory state, which, in turn, drives neutrophils to prime and release NETs, which drive the development of a hypercoagulable state. Intervening in this process may be a viable means of disrupting these undesirable coagulation dynamics in stage III/IV OSCC patients.

Mechanisms and management of coagulopathy in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a subtype of leukemia which is associated with unique and distinctive coagulopathy. In the absence of treatment it is rapidly fatal and even after initiation of therapy the major cause of early mortality is related to hemorrhagic complications. The coagulopathy can be exacerbated with the start of treatment. In the absence of early hemorrhage related deaths the probability of cure exceeds 90% in low and intermediate risk patients and 80% even in high risk patients, highlighting the importance of understanding the pathophysiology of this complication and instituting prompt and appropriate management strategies. The coagulopathy in APL is complex and results from a combination of thrombocytopenia, disseminated intravascular coagulation and hyperfibronlysis. Recently the effect of all-trans retinioc acid (ATRA) induced ETosis on exacerbating coagulopathy in the first few days after starting therapy with this agent raises the potential for potentially novel strategies to reduce the risk of hemorrhage. Currently management is mainly related to rapid initiation of therapy with ATRA along with appropriate and adequate replacement of blood products to correct the coagulopathy. There is limited role for the use of low dose anti-coagulants and anti-fibrinolytic agents in the initial management of this disease. There is limited data on the use of rFVIIa or the use of global tests of hemostasis in the management of this condition.

Characteristics of fibrinolytic disorders in acute promyelocytic leukemia

OBJECTIVES

Catastrophic hemorrhage remains the main cause of acute promyelocytic leukemia (APL) treatment failure. This study was aimed to study the pathogenesis of coagulopathy in patients with APL.

METHODS

Multiple procoagulant and profibrinolytic parameters in plasma and peripheral leukocytes from 24 patients with newly diagnosed APL accompanied by coagulopathy before and after arsenic trioxide (ATO) treatment were evaluated.

RESULTS

Prior to the treatment, the patients had elevated D-dimer and decreased fibrinogen levels. Plasma urokinase-type plasminogen activator receptor (uPAR) and plasmin-ɑ₂ antiplasmin complexes (PAP) levels, plasmin (Pn) activity, and cell surface levels of urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) were significantly higher; plasma plasminogen activator inhibitor-1 (PAI-1) levels and plasminogen (Pg) activity were significantly decreased; plasma plasminogen activator (PA) activity, uPA and tPA levels; and cell surface levels of uPAR and annexin II were not significantly different from levels in the control group. During ATO treatment, both patients' plasma PA activity and uPAR on leukocytes gradually increased, annexin II on leukocytes increased initially and decreased afterwards, and tPA and uPA on leukocytes remained consistently higher in the patients than in the controls. Other parameters gradually tended toward normal values.

CONCLUSIONS

In APL, activated coagulation system activated fibrinolytic system, and increased uPAR levels could contribute to the hyperfibrinolysis. Annexin II might not be involved in the coagulopathy.

Arsenic trioxide promoting ETosis in acute promyelocytic leukemia through mTOR-regulated autophagy

Despite the high efficacy and safety of arsenic trioxide (ATO) in treating acute promyelocytic leukemia (APL) and eradicating APL leukemia-initiating cells (LICs), the mechanism underlying its selective cytotoxicity remains elusive. We have recently demonstrated that APL cells undergo a novel cell death program, termed ETosis, through autophagy. However, the role of ETosis in ATO-induced APL LIC eradication remains unclear. For this study, we evaluated the effects of ATO on ETosis and the contributions of drug-induced ETosis to APL LIC eradication. In NB4 cells, ATO primarily increased ETosis at moderate concentrations (0.5–0.75 μM) and stimulated apoptosis at higher doses (1.0–2.0 μM). Furthermore, ATO induced ETosis through mammalian target of rapamycin (mTOR)-dependent autophagy, which was partially regulated by reactive oxygen species. Additionally, rapamycin-enhanced ATO-induced ETosis in NB4 cells and APL cells from newly diagnosed and relapsed patients. In contrast, rapamycin had no effect on apoptosis in these cells. We also noted that PML/RARA oncoprotein was effectively cleared with this combination. Intriguingly, activation of autophagy with rapamycin-enhanced APL LIC eradication clearance by ATO in vitro and in a xenograft APL model, while inhibition of autophagy spared clonogenic cells. Our current results show that ATO exerts antileukemic effects at least partially through ETosis and targets LICs primarily through ETosis. Addition of drugs that target the ETotic pathway could be a promising therapeutic strategy to further eradicate LICs and reduce relapse.

Phosphatidylserine-exposing blood and endothelial cells contribute to the hypercoagulable state in essential thrombocythemia patients

The mechanisms of thrombogenicity in essential thrombocythemia (ET) are complex and not well defined. Our objective was to explore whether phosphatidylserine (PS) exposure on blood cells and endothelial cells (ECs) can account for the increased thrombosis and distinct thrombotic risks among mutational subtypes in ET. Using flow cytometry and confocal microscopy, we found that the levels of PS-exposing erythrocytes, platelets, leukocytes, and serum-cultured ECs were significantly higher in each ET group [JAK2, CALR, and triple-negative (TN) (all P < 0.001)] than those in controls. Among ET patients, those with JAK2 mutations showed higher levels of PS-positive erythrocytes, platelets, neutrophils, and serum-cultured ECs than TN patients or those with CALR mutations, which show similar levels. Coagulation function assays showed that higher levels of PS-positive blood cells and serum-cultured ECs led to markedly shortened coagulation time and dramatically increased levels of FXa, thrombin, and fibrin production. This procoagulant activity could be largely blocked by addition of lactadherin (approx. 70% inhibition). Confocal microscopy showed that the FVa/FXa complex and fibrin fibrils colocalized with PS on ET serum-cultured ECs. Additionally, we found a relationship between D-dimer, prothrombin fragment F1 + 2, and PS exposure. Our study reveals a previously unrecognized link between hypercoagulability and exposed PS on cells, which might also be associated with distinct thrombotic risks among mutational subtypes in ET. Thus, blocking PS-binding sites may represent a new therapeutic target for preventing thrombosis in ET.

Complications and management of coagulation disorders in leukemia patients

Patients with leukemia are predisposed to various coagulation abnormalities. Thrombosis and bleeding continue to be a major cause of morbidity and mortality in leukemias. The pathophysiology of these disorders is unique, and not only the disease but also the treatment and other factors play a role. There has been an increase in the understanding of these disorders in leukemias. However, it is still difficult to predict when and which patients will have these complications. The evidence for the management of coagulation abnormalities in leukemias is still evolving and not as established as in solid malignancies. The management of these disorders is complex, and making clinical decisions is often challenging. In the era of specialization, where there are different hematologists looking after benign- and malignant-hematology patients, opinions of thrombosis experts are often sought by leukemia specialists. This review aims to bridge the gap in the knowledge of these disorders between these specialists.