Our study provides evidence that MP formation due to RBC storage might propagate coagulation not only by exposing phosphatidylserine, but also by initiating thrombin generation independently of tissue factor in a FXI -dependent manner.
The frequent serious bleeding and thrombotic complications in acute promyelocytic leukemia (APL) are major causes of early mortality, but the complex mechanisms causing the bleeding have not been completely elucidated. Because microparticles (MPs) are known to be elevated in thromboembolic disorders, we hypothesized a role for MPs in the pathogenesis of coagulopathy in APL. MPs were isolated from 30 APL patients and 20 healthy subjects and from cultured NB4/APL cells. The morphology of the MPs was examined, and they were quantified and analyzed for their thrombin-generating potential. We confirmed the existence of promyelocytic-derived MPs by morphology using transmission electron microscopy and laser scanning confocal microscopy. Counts of MPs in APL were elevated and were typically from promyelocytic cells (CD33(+) TF(+) MPs). Importantly, the CD33(+) MPs strongly correlated with patient leukocyte count (R = 0.64, p = 0.002) and D-dimer (R = 0.51, p = 0.0038). Moreover, the MPs from patients with APL decreased the coagulation times and induced thrombin generation. APL MP-associated thrombin generation was reduced by 54 % when the extrinsic pathway was blocked using an anti-human tissue factor (TF) antibody. However, neither anti-factor XI nor anti-tissue factor pathway inhibitor had any significant inhibitory effect. Our results show that the procoagulant state in APL is partially due to the TF-dependent procoagulant properties of circulating promyelocytic-derived MPs. TF(+) MPs may be a novel potential risk factor for coagulopathy in APL.
Despite the constant emergence of new methods for the treatment of multiple myeloma (MM), relapse and drug resistance still exist, especially in MM with p53 mutations. Arsenic trioxide (ATO) can be used in MM treatment, but this single drug has poor effectiveness and also side effects. Curcumin is a safe and effective compound that can enhance the anticancer effects of many drugs. Previous studies have suggested that tumor cell sensitivity to ATO is related to the intracellular arsenic content, and aquaporin 9 (AQP9) is the key factor that determines intracellular arsenic content. This study aimed to explore whether curcumin can increase ATO cytotoxicity in MM and whether the mechanism is related to the regulation of intracellular arsenic content. U266 was treated with ATO, curcumin, and their combination, and cell proliferation, apoptosis, and intracellular arsenic content were detected by CCK-8 assay, flow cytometry, and HPLC-ICP-MS, respectively. AQP9 mRNA and protein levels were detected by qPCR and western blotting. The levels of Mcl-1, Bcl-2, Bax, caspase-3, and cleaved caspase-3 protein were detected by western blotting. ATO-induced cytotoxicity to U266 occurred in a time- and dose-dependent manner, but the therapeutic efficacy at low drug concentrations was modest. The arsenic content in U266 was lower than that in NB4, and the arsenic uptake by U266 was concentration-dependent. The expression levels of AQP9 mRNA and AQP9 protein in U266 were lower than those in NB4. Curcumin significantly enhanced the lethality of ATO to U266. The arsenic content in U266 in the combined drug group increased significantly compared with ATO treatment alone. After curcumin treatment, the AQP9 mRNA and AQP9 protein expression levels in U266 also increased. Compared with the control group, the expression of antiapoptotic proteins Mcl-1 and Bcl-2 decreased, the expression of proapoptotic protein Bax increased, the ratio of Bax/Bcl-2 increased, and the expression of caspase-3 decreased and cleaved caspase-3 increased in the combined drug groups. Curcumin can enhance the killing effects of ATO on U266 by increasing the intracellular arsenic content, which may be related to the upregulation of AQP9 expression. The combination of these two drugs is expected to be a potential clinical treatment for MM.
: The introduction of new agents in multiple myeloma therapy has increased the overall response rate and improved clinical outcomes, but the increased risk of thrombotic complications impairs the quality of life of patient and the optimal thromboprophylaxis remains unknown. Increasing evidence has shown that statins can prevent venous thrombosis. Hence, we investigated the effects of simvastatin on multiple myeloma serum-related haemostatic imbalance in endothelial cells in vitro. The effects of simvastatin on procoagulant and anticoagulant protein expression were assessed on mixed multiple myeloma serum-treated human umbilical vein endothelial cells (HUVECs). The activity of these proteins was measured by thrombin generation and protein C activation assay. Then, the effects of extracellular signal-regulated kinase (ERK) 1/2 on endothelial activation were assessed by western blot and inhibition assay. We found that simvastatin inhibited multiple myeloma serum-induced expression of procoagulant protein tissue factor and phosphatidylserine and generation of thrombin on HUVECs. In contrast, simvastatin increased multiple myeloma serum-inhibited expression of anticoagulant protein endothelial protein C receptor and activation of protein C on HUVECs. Moreover, simvastatin reversed the multiple myeloma serum-induced prothrombotic phenotype, at least in part, via the inhibition of ERK 1/2 activation in endothelial cells. This study supports the beneficial effects of simvastatin on multiple myeloma serum-induced endothelial haemostatic imbalance, which suggests that simvastatin may serve as a new and appropriate antithrombotic approach for multiple myeloma patients.
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