In resting platelets, the 17 ^th domain of filamin a (FLNa17) constitutively binds to the platelet membrane glycoprotein Ibα (GPIbα) at its cytoplasmic tail (GPIbα-CT) and inhibits the downstream signal activation, while the binding of ligand and blood shear force can activate platelets. To imitate the pull force transmitted from the extracellular ligand of GPIbα and the lateral tension from platelet cytoskeleton deformation, two pulling modes were applied on the GPIbα-CT/FLNa17 complex, and the molecular dynamics simulation method was used to explore the mechanical regulation on the affinity and mechanical stability of the complex. In this study, at first, nine pairs of key hydrogen bonds on the interface between GPIbα-CT and FLNa17 were identified, which was the basis for maintaining the complex structural stability. Secondly, it was found that these hydrogen bonding networks would be broken down and lead to the dissociation of FLNa17 from GPIbα-CT only under the axial pull force; but, under the lateral tension, the secondary structures at both terminals of FLNa17 would unfold to protect the interface of the GPIbα-CT/FLNa17 complex from mechanical damage. In the range of 0~40 pN, the increase of pull force promoted outward-rotation of the nitrogen atom of the 563 ^rd phenylalanine (PHE ⁵⁶³-N) at GPIbα-CT and the dissociation of the complex. This study for the first time revealed that the extracellular ligand-transmitted axial force could more effectively relieve the inhibition of FLNa17 on the downstream signal of GPIbα than pure mechanical tension at the atomic level, and would be useful for further understanding the platelet intracellular force-regulated signal pathway.
Filamins/metabolism* ; Platelet Glycoprotein GPIb-IX Complex/metabolism* ; Molecular Dynamics Simulation ; Ligands ; Protein Binding ; Blood Platelets/metabolism* ; von Willebrand Factor/metabolism*

Platelets not only have hemostatic function, but can also directly or indirectly recognize pathogenic microorganisms and the signals they produce to capture and destroy them through membrane receptors. They can collaborate with various components of the body's immune system by releasing of intraplatelet particulate matter, cytokines and chemokines to perform bactericidal functions. And it can also play a bactericidal role by swallowing pathogens, releasing antimicrobial proteins and chemokines and activating and enhancing other specialized anti-inflammatory cells bactericidal effect, such as leukocytes and so on. However, the bacteriostatic composition and bacteriostatic mechanism of platelets remain unclear, so attention should be paid to the immune mechanism and bacteriostatic effect of platelets.
Blood Platelets ; Anti-Bacterial Agents/pharmacology* ; Cytokines ; Leukocytes ; Particulate Matter

OBJECTIVE: To investigate the correlation of peripheral blood platelet/lymphocyte ratio (PLR) with Treg and Th17 and its influence on prognosis in newly diagnosed multiple myeloma (MM). METHODS: One hundred thirty-five newly diagnosed multiple myeloma patients admitted to the Department of Hematology of Zhengzhou People's Hospital from June 2015 to October 2022 were selected as MM group. Clinical data included sex, age, immune typing, ISS stage, blood calcium (Ca), albumin (ALB), hemoglobin (Hb), PLR, LDH, β₂ microglobulin (β₂-MG), Treg and Th17 levels. Sixty healthy volunteers who underwent physical examination in our hospital during the same period were selected as the control group. PLR, Treg and Th17 levels in MM group and control group were compared. Pearson was used to analyze the correlation between PLR and Treg, Th17. The relationship between MM patients with different PLR and clinical features and prognosis was analyzed. RESULTS: The PLR and Th17 of MM patients were significantly higher than that of control group, and Treg was significantly lower than that of control group (P<0.05). In MM patients, PLR was negatively correlated with Treg (r=-0.616), and PLR was positively correlated with Th17 (r=0.555). Using mean PLR=132.72 as the boundary, 135 MM patients were divided into high PLR group (n=54) and low PLR group (n=81). In MM patients with high PLR, ISS stage, ALB and Treg were significantly higher than those in low PLR group, while Th17 was significantly lower than those in low PLR group (P<0.05). By univariate and COX regression analysis, PLR was an independent prognostic risk factor for newly diagnosed MM patients (P<0.05). MM patients with high PLR had better PFS and OS, and the difference was statistically significant compared with MM patients with low PLR (P<0.05). 65 patients admitted from June 2015 to December 2018 were used as the training set, and 70 patients admitted from January 2019 to October 2022 were used as the validation set. The OS of MM patients with different PLR were compared respectively. The results showed that the conclusions of the training set and the validation set were consistent. PLR with high expression had higher OS (P<0.01). CONCLUSION PLR is correlated with Treg and Th17 in newly diagnosed MM patients, and high PLR has better prognosis. PLR can be used to evaluate the prognosis of MM patients.
Humans ; Multiple Myeloma/diagnosis* ; Blood Platelets ; T-Lymphocytes, Regulatory ; Prognosis ; Th17 Cells ; Retrospective Studies

OBJECTIVE: To investigate the changes of platelet count (PLT), plateletcrit (PCT), mean platelet volume (MPV) and platelet distribution width (PDW) before and after apheresis platelet transfusion, the correlation between the parameters and their clinical significance. METHODS: A total of 38 patients who received apheresis platelet transfusion were selected, their results of blood routine test closest to the time point of apheresis platelet transfusion were consulted from hospital information system and the changes of PLT, PCT, MPV and PDW were compared before and after transfusion. The correlation between above parameters was analyzed. The correlation of body mass index (BMI) with the increased multiple and increased value after platelet infusion was also analyzed. RESULTS: Compared with pre-infusion, PLT and PCT significantly increased (both P <0.001) while MPV and PDW showed no significant difference after apheresis platelet transfusion (P >0.05). The difference of PLT and PCT before and after apheresis platelet transfusion had no correlation with PLT and PCT before transfusion (r =0.002, r =0.001), while the difference of MPV and PDW was negatively correlated with MPV and PDW before transfusion (r =-0.462, r =-0.610). The PLT growth rate was positively correlated with PCT growth rate before and after apheresis platelet transfusion (r =0.819). BMI was positively correlated with the increased multiple of PLT after infusion (r =0.721), but not with the increased value of PLT after infusion (r =0.374). CONCLUSION Apheresis platelet transfusion can cause platelet parameters change and shows different characteristics. Characteristic changes of platelet parameters and their correlation can be used as reference indices to evaluate the efficacy of apheresis platelet transfusion.
Humans ; Mean Platelet Volume ; Platelet Transfusion ; Blood Platelets ; Platelet Count/methods* ; Blood Component Removal

Humans ; Female ; Blood Platelets ; Ovarian Neoplasms/diagnosis*

Activated platelets may interact with various types of leukocytes such as monocytes, neutrophils, dendritic cells, and lymphocytes, trigger intercellular signal transduction, and thus lead to thrombosis and synthesis of massive inflammatory mediators. Elevated levels of circulating platelet-leukocyte aggregates have been found in patients with thrombotic or inflammatory diseases. This article reviews the latest research on the formation, function, and detection methods of platelet-leukocyte aggregates and their role in the onset of Kawasaki disease, so as to provide new ideas for studying the pathogenesis of Kawasaki disease.
Humans ; Mucocutaneous Lymph Node Syndrome/etiology* ; Blood Platelets ; Inflammation Mediators ; Leukocytes ; Neutrophils

OBJECTIVE: To explore the effects of Ena/VASP gene family on the expression of glycoprotein (GP) Ib-IX complex in human megakaryoblastic leukemia Dami cells. METHODS: SiRNAs targeting Ena/VASP gene family were designed and synthesized to interfere Enah, EVL and VASP gene expression. When the siRNAs were transfected into Dami cells by using Lipofectamine^TM 2000 for 48 h, the expression of GPIb-IX complex was detected by quantitative real-time PCR, Western blot and flow cytometry. RESULTS: We successfully established siVASP , siEVL and si Enah Dami cell lines. And it was found that the expression of GPIb-IX complex had no evident reduction in siEVL or siVASP Dami cells at both mRNA and protein level, while the total protein and membrane protein of GPIb-IX complex were obviously reduced when Enah was knocked down. CONCLUSION Enah could affect the expression of GPIb-IX complex in human megakaryoblastic leukemia Dami cells, but the underlying mechanism still needs to be further explored.
Humans ; Cell Line ; Platelet Glycoprotein GPIb-IX Complex/metabolism* ; Leukemia/metabolism* ; Blood Platelets/metabolism*

OBJECTIVE: To study the effect of gradient shear stress on platelet aggregation by microfluidic chip Technology. METHODS: Microfluidic chip was used to simulate 80% fixed stenotic microchannel, and the hydrodynamic behavior of the stenotic microchannel model was analyzed by the finite element analysis module of sollidwork software. Microfluidic chip was used to analyze the adhesion and aggregation behavior of platelets in patients with different diseases, and flow cytometry was used to detect expression of the platelet activation marker CD62p. Aspirin, Tirofiban and protocatechuic acid were used to treat the blood, and the adhesion and aggregation of platelets were observed by fluorescence microscope. RESULTS: The gradient fluid shear rate produced by the stenosis model of microfluidic chip could induce platelet aggregation, and the degree of platelet adhesion and aggregation increased with the increase of shear rate within a certain range of shear rate. The effect of platelet aggregation in patients with arterial thrombotic diseases were significantly higher than normal group (P<0.05), and the effect of platelet aggregation in patients with myelodysplastic disease was lower than normal group (P<0.05). CONCLUSION The microfluidic chip analysis technology can accurately analyze and evaluate the platelet adhesion and aggregation effects of various thrombotic diseases unde the environment of the shear rate, and is helpful for auxiliary diagnosis of clinical thrombotic diseases.
Humans ; Microfluidics ; Platelet Adhesiveness ; Platelet Aggregation ; Blood Platelets/metabolism* ; Platelet Aggregation Inhibitors/pharmacology* ; Platelet Activation/physiology* ; Thrombosis

OBJECTIVE: To investigate the effect and relative mechanism of Recombinant Human Thrombopoietin (rhTPO) on long-term hematopoietic recovery in mice with acute radiation sickness. METHODS: Mice were intramuscularly injected with rhTPO (100 μg/kg) 2 hours after total body irradiation with ⁶⁰Co γ-rays (6.5 Gy). Moreover, six months after irradiation, peripheral blood, hematopoietic stem cells (HSC) ratio, competitive transplantation survival rate and chimerization rate, senescence rate of c-kit⁺ HSC, and p16 and p38 mRNA expression of c-kit⁺ HSC were detected. RESULTS: Six months after 6.5 Gy γ-ray irradiation, there were no differences in peripheral blood white blood cells, red blood cells, platelets, neutrophils and bone marrow nucleated cells in normal group, irradiated group and rhTPO group (P>0.05). The proportion of hematopoietic stem cells and multipotent progenitor cells in mice of irradiated group was significantly decreased after irradiation (P<0.05), but there was no significant changes in rhTPO group (P>0.05). The counts of CFU-MK and BFU-E in irradiated group were significantly lower than that in normal group, and rhTPO group was higher than that of the irradiated group(P<0.05). The 70 day survival rate of recipient mice in normal group and rhTPO group was 100%, and all mice died in irradiation group. The senescence positive rates of c-kit⁺ HSC in normal group, irradiation group and rhTPO group were 6.11%, 9.54% and 6.01%, respectively (P<0.01). Compared with the normal group, the p16 and p38 mRNA expression of c-kit⁺ HSC in the irradiated mice were significantly increased (P<0.01), and it was markedly decreased after rhTPO administration (P<0.01). CONCLUSION The hematopoietic function of mice is still decreased 6 months after 6.5 Gy γ-ray irradiation, suggesting that there may be long-term damage. High-dose administration of rhTPO in the treatment of acute radiation sickness can reduce the senescence of HSC through p38-p16 pathway and improve the long-term damage of hematopoietic function in mice with acute radiation sickness.
Humans ; Mice ; Animals ; Thrombopoietin/metabolism* ; Hematopoietic Stem Cells ; Blood Platelets ; Recombinant Proteins/therapeutic use* ; Radiation Injuries ; RNA, Messenger/metabolism*

OBJECTIVE: To explore the regulation of mitochondria on platelet apoptosis and activation, and the relationship between platelet apoptosis and activation. METHODS: Platelets were isolated from peripheral venous blood of healthy volunteers. Cyclosporin A (CsA), which has a protective effect on the function of platelet mitochondria, BAPTA, which can chelate calcium ions across membranes in platelets, and NAC, an antioxidant that reduces the level of intracellular reactive oxygen species, were selected for coincubation with washed platelets, respectively. By flow cytometry, platelet aggregator was used to detect the changes of platelet mitochondrial function and platelet activation indexes after different interventions. RESULTS: H89, staurosporine, and A23187 led to platelet mitochondrial abnormalities, while CsA could effectively reverse the decline of platelet mitochondrial membrane potential caused by them. Antioxidant NAC could reverse platelet mitochondrial damage correspondingly, and completely reverse platelet shrinkage and phosphatidylserine eversion induced by H89. BAPTA, prostaglandin E1, acetylsalicylic acid and other inhibitors could not reverse the decline of platelet mitochondrial membrane potential. CONCLUSION Mitochondrial function plays an important role in platelet apoptosis and activation. Abnormal mitochondrial function causes the imbalance of reduction/oxidation state in platelets, which leads to platelet apoptosis. Platelet apoptosis and activation are independent signal processes.
Humans ; Blood Platelets/metabolism* ; Antioxidants/pharmacology* ; Mitochondria/physiology* ; Platelet Activation ; Apoptosis ; Membrane Potential, Mitochondrial ; Reactive Oxygen Species/pharmacology*