Effects of different group B streptococci strains on platelet activation

AIM: To explore the ability of different group B streptococci (GBS) strains on inducing platelet activation. METHODS: Six strains of GBS, separated from the septic patients with thrombocytopenia, were used as the inducers. Light transmission aggregometry was used to measure platelet aggregation. Scanning electron microscopy (SEM) was performed to investigate the interaction of platelets with bacteria. The expression of platelet CD62P, Toll-like receptor 2 (TLR2) and TLR4 was determined by flow cytometry and Western blotting. Furthermore, the activity of platelet TLR2 (or TLR4) was blocked by anti-TLR2 (or anti-TLR4) monoclonal antibody, and the platelet aggregation induced by GBS was detected. RESULTS: Only 3 of 6 GBS strains isolated from the septic patients induced platelet aggregation and up-regulated the expression of CD62P and TLR2 in the platelets (P < 0.05), but not TLR4. Incubation with anti-TLR2 antibody, but not anti-TLR4 antibody, significantly blocked platelet aggregation induced by GBS.CONCLUSION: Some GBS strains from the patients are able to trigger platelet activation in vitro, and platelet TLR2 may play an important role in the interaction between GBS and platelets.     

Expression of TCR Vβ subfamily in patients with idiopathic thrombocytopenic purpura

AIM: To investigate the expression of TCR Vβ subfamily in T cells in patients with idiopathic thrombocytopenic purpura (ITP). METHODS: The TCR Vβ 24 subfamily genes were amplified in peripheral blood mononuclear cells from 5 cases with ITP using RT-PCR, to observe the usage of TCR Vβ repertoire. 10 normal individuals served as controls. RESULTS: Only 4-11 Vβ subfamily in T cells were identified in ITP cases. The frequent expressions of Vβ subfamilies were Vβ2 (100%), Vβ3 (100%), Vβ19 (80%) and Vβ21 (80%), while the expression of Vβ4, Vβ6-12, Vβ17, Vβ20 and Vβ24 were not detected. All 24 Vβ subfamilies were detected in samples from normal individuals. CONCLUSION: The restricted expression of TCR Vβ subfamilies is one of the T-cell immune features in patients with ITP, indicating that it may be related to the disorder of cellular immune function in ITP.     

Effect of mesenchymal stem cells on secreting function of T lymphocytes from patients with idiopathic thrombocytopenic purpura in vitro

AIM: To analyze the effect of mesenchymal stem cells (MSCs) on secreting cytokines by T lymphocytes from patients with idiopathic thrombocytopenic purpura (ITP) in vitro.METHODS: Human bone marrow-derived MSCs were isolated by Ficoll Hypaque and cultured for proliferating to passage cells. Allogeneic T lymphocytes of ITP were isolated from peripheral blood by Ficoll Hypaque and nylon cotton column. Then the stromal feeder layers of different numbers (2×103, 1×104, 5×104 per well) of MSCs treated with mitomycin were co-cultured with above-mentioned T lymphocytes. The supernatant were respectively collected on day 2, 4 and 6 after co-culture, then the levels of IL-2, IFN-γ, IL-4, IL-10 secreted by T lymphocytes were measured by enzyme linked immunosorbent assay (ELISA) dynamically.RESULTS: The levels of IL-2 and IFN-γ secreted by T cells from ITP were higher than those from normal control (P<0.05, respectively). Inversely, IL-4 and IL-10 were lower than those in normal control (P<0.05, respectively). After co-cultured with T lymphocytes, MSCs significantly inhibited the cytokine levels of IL-2 and IFN-γ secreted by T lymphocytes from ITP or health adults (P<0.05, respectively) in a dose dependent manner (P<0.05, respectively), and the effect was more obvious when co-cultured for 4 days or 6 days than that for 2 days (P<0.05, respectively). However, MSCs significantly promoted the releases of IL-4 and IL-10 by T lymphocytes from ITP patients (P<0.05, respectively) in a dose dependent manner (P<0.05, respectively), and the effect on IL-10 was in a time dependent way (P<0.05), while the effect on IL-4 had no obvious difference among 2 d, 4 d and 6 d(P>0.05). As for health control group, when cell numbers exceeded above 1×104, MSCs obviously promoted IL-4 and IL-10 levels secreted by T lymphocytes (P<0.05) in a dose dependent manner (P<0.05), and both of the effects were more noticeable when co-cultured for 4 d or 6 d than that for 2 d(P<0.05, respectively).CONCLUSION: MSCs regulate the balance between Th1 and Th2 reaction and partly correct ITP Th1 polarization in vitro.     

Expression of Th cytokines in peripheral blood before and after splenectomy in immune thrombocytopenia patients

AIM: To investigate the changes of Th cytokines before and after splenectomy in immune thrombocytopenia (ITP) patients. METHODS: The QuantiGene Plex method was used to measure the mRNA expression of Th1, Th2 (IL-4, IL-5, IL-6 and IL-10), Th3 (transforming growth factor β₁,TGF-β₁), and Th17 (IL-17) cytokines in peripheral blood of ITP patients before and after laparoscopic splenectomy and those in peripheral blood of healthy controls. RESULTS: The mRNA level of IL-2 was significantly decreased in ITP patients before operation compared with the healthy controls, whereas IL-17 was obviously over-expressed. No significant difference of the other cytokines between preoperative group and the normal controls was found. After splenectomy, the expression levels of both IL-2 and TGF-β₁ were significantly higher than those in preoperative group and the normal controls. IL-2 was also significantly increased after operation, but was still lower than that in the normal controls. No significant difference of other cytokines between postoperative group and healthy controls was observed. In addition, The Th1 cytokines (IL-2 and IFN-γ) were found to be positively correlated (r=0.647, P<0.01) in preoperative patients, while no correlation was found between the other cytokines. There was a positive correlation between IL-2 and IFN-γ (r=0.787, P<0.01) in postoperative patients. IL-17 also had positive correlations with IL-2 (r=0.554,P<0.01) and IFN-γ (r=0.461,P<0.05) in ITP patients after operation, respectively. CONCLUSION: There is an imbalance of Th cytokines in ITP patients. The mechanism of splenectomy for treating ITP may be associated with the balance regulation of Th cytokines.     

Study on biological activity of thrombopoietinⅡ in vivo

AIM: To investigate the biological activity of thrombopoietin Ⅱ(TPOⅡ) in vivo, which consists of two new kinds of ligand binding with thrombopoietin receptor. METHODS: Purified ligandⅠof TPOⅡ, artificial compound ligandⅡ of TPOⅡand rhTPO were injected into purebred Babl/c mice respectively in 7 days by intraperitoneal injection once for a day. Then the biological activity of TPOⅡ was analyzed by measuring peripheral platelet counts by the end of the seventh day. RESULTS: On the seventh day, the platelet counts of mice treated by ligandⅠof TPOⅡ were higher than that in the negative control group(P＜0.05), while not significantly different from the platelet counts of mice treated by rhTPO(P＞0.05). On the fourteenth day, the platelet counts increased in two all experimental groups of TPOⅡcompared with negative control group(P＜0.01), while not significantly different from the platelet counts of mice treated by rhTPO too(P＞0.05). Moreover the platelet counts of mice in two experimental groups of TPOⅡ and the positive group showed increase with experimental days. CONCLUSION: The purified ligandⅠof TPOⅡ had obvious activity in increasing platelet production, which is not different from the effect of rhTPO.     

Application of anti-CD20 antibody in hematopoietic stem cell transplantation for sensitized recipients

AIM: To find a strategy for enhancing engraftment of hematopoietic stem cell in sensitized recipients and to study the effects of anti-CD20 antibody in hematopoietic stem cell transplantation. METHODS: BALB/c mice were sensitized by transfusions of allogeneic spleen cells on 14 d and 7 d. Anti-CD20 antibody (2 mg/mouse) was intravenously injected into sensitized recipients on 11 d. The recipients were used as experimental group, while RPMI-1640 medium (0.2 mL/mouse) was used as control. The sera and splenocytes obtained from the recipients were tested for donor reactive antibody and CD19+ B cells on 0 d. In addition, the recipients were transplanted with 1×107 C57BL/6 bone marrow cells after lethal irradiation on 0 d. The survival rates were observed and blood counts were studied post transplantation. RESULTS: The cytotoxic index in the experimental group and control group were (37.00±3.46)% and (51.80±3.49)%, respectively, and the differences were significant (P<0.01). The percentages of CD19+ B cells in experimental group and control group were (17.32±3.02)% and (34.26±2.87)%, respectively, and the differences were significant (P<0.01). All the recipients in both experimental group and control group died about 14 d post transplantation. The median time was 13 d and 11 d in experimental group and control group, respectively, and no significant difference was found between these two groups (P>0.05). Moreover, a rapid disappearance was observed in the white blood counts, hemoglobin, and platelet of dying animals, indicating the animals died from hematopoietic failure. CONCLUSION: Anti-CD20 antibody is able to deplete B cells and reduce the level of antibody in sensitized recipients, but it can’t enhance the engraftment of allogeneic hematopoietic stem cells in the sensitized recipients.     

Establishment and assessment of a method for acid elution of platelet HLA class I antigens

AIM: To establish an effective method for acid elution of platelet HLA class I antigens, and to evaluate the optimal condition and the feasibility of clinical application of the acid-elution technique. METHODS: Platelets were treated with citric acid buffer at different pH levels (pH=2, 3, 5, 7). Expression of HLA class I antigens and P-selectin (CD62P) on the platelet surface was analyzed by multicolor flow cytometry. The proportion of early apoptotic platelets was detected by Annexin V staining. The maximum platelet aggregation rate was determined by electrical impedance aggregometry.RESULTS: With the decrease in the pH levels of the citric acid buffer (from pH=7 to pH=2), the expression of HLA class I antigens on the platelet surface was remarkably decreased. However, the rates of platelets activation (CD62P expression) and early apoptosis (Annexin V expression) were both significantly increased. Compared with PBS, treatment of the platelets with citric acid buffer at pH 3.0 remarkably reduced the expression of platelet HLA-class I antigens (P<0.05). Although the rates of the platelet activation and apoptosis were also significantly increased (P<0.05), the aggregation of platelet was not remarkably reduced (P>0.05).CONCLUSION: Acid elution of platelet HLA-class I antigens with citric acid buffer at pH 3.0 at 0 ℃ can be use as an attempt to produce HLA-eluted platelets. This technique of acid-elution needs further improvement and standardization before clinical use.     

Effect of anti-CD59 on CVF-induced platelet activation

AIM:To study the reactions of human platelet to active complement and the effects of anti-CD59 on human platelet activation induced by complement.METHODS:By applying CVF to activate complement, the platelet aggregation and release reactions induced by activated complement with or without appling anti-CD59 with different doses to block the complement modulative protein CD59 in healthy individuals, were observed.RESULTS:CVF induced platelet release and significant and lasting metamorphosis in healthy individuals, but platelet aggregation was not observed. CVF-induced platelet metamorphosis showed positive linear correlation to lg concentration of CVF (r=0.970. P<0.01. n=36). Anti-CD59 enhanced CVF-induced platelet shape change with a dose-dependent manner. The max enhancive ratio of platelet shape change was 1.36(P<0.01). Anti-CD59 enhanced platelet ATP release induces by CVF.CONCLUSION:Complement activated by CVF induces significant and lasting platelet metamorphosis and release reaction, but dose not induce platelet aggregation in healthy adult males. Anti-CD59 promotes the platelet reactions induced by active complement.     

Effect of ERK1/2 phosphorylation on the aggregation of the rat platelets in vitro

AIM: To study the influence of PD098059 on the rat platelet aggregation rate and the phosphorylation of ERK1/2 induced by the different agonists, and to observe the effects of phosphorylation of ERK1/2 on the platelet aggregation. METHODS: The maximal aggregation rate (MAR) was measured by nephelometry. The inhibitory rate of PD098059 and the appearing time of MAR were also observed. ERK1/2 phosphorylation was detected by Western blot. RESULTS: The phosphorylation of ERK1/2 was detected during aggregation induced by thrombin and ADP. PD098059 inhibited the MAR and phosphorylation of ERK1/2. Effects of PD098059 were different on the aggregation induced by thrombin and ADP. CONCLUSIONS: The phosphorylation of ERK1/2 is one of the cellular signal transduction mechanisms of platelets aggregation. Phosphorylation of ERK1/2 plays different roles during the platelet aggregation induced by thrombin and ADP.     

Effect of sodium ferulate on heat shock protein 27 phosphorylation in vascular smooth muscle cells

AIM: To investigate the effect of sodium ferulate on phosphorylation of heat shock protein 27 (HSP27) in vascular smooth muscle cells (VSMCs) induced by angiotensin II (AngII) and platelet derived growth factor-BB (PDGF-BB).METHODS: Cultured VSMCs derived from rat thoracic aorta were used.The activity of HSP27 was evaluated by Western blotting with specific phospho-HSP27 antibody.RESULTS: The phosphorylation of HSP27 in response to AngII and PDGF-BB was suppressed by sodium ferulate in a dose-dependent manner,with maximal inhibition rates of 39.0% (P<0.05) and 56.8% (P<0.01) respectively at concentration of 10-4 mol/L.CONCLUSION: HSP27 phosphorylation induced by AngII and PDGF-BB in VSMCs may be significantly inhibited by sodium ferulate.     

Ultrastructure of epicuticular wax aggregates during fruit development in apple (Malus domestica Borkh.)

Summary

Development of wax platelets on the surface of ‘Delicious’ (Malus domestica Borkh.) apple fruit was investigated throughout the growing season using field emission scanning electron microscopy. At 5,000 and greater, wax crystalline structures appeared to be composed of microtubules (MT), aggregates of individual MT to form single platelets, and of one or more platelets. The thickness of a single wax platelet ranged from 116–128 nm, approximately the diameter of a single MT; whereas multiple-platelet aggregates ranged in thickness from 307–428 nm. Individual platelets, multiple platelet aggregates and MT were visible throughout fruit development, as well as on different apple cultivars. Examination of the cuticle from young fruitlets (receptacle diameter = 3 mm) of ‘Chinese Crabapple’ (M. hupehensis Rehd.), which develops without trichomes, best demonstrated early platelet formation. A model for wax platelet and cuticle development on apple is proposed based on these data.     

Effects of Tongxinluo on activation of platelet in rabbit model of atherosclerosis

AIM: To study the effects of Tongxinluo on the activation of platelets in a rabbit model of atherosclerosis. METHODS: New Zealand rabbits were randomly divided into 7 groups: normal group, model group, the groups treated with high, medium and low doses of Tongxinluo micropowder (0.15, 0.3 and 0.6 g·kg^-1·d^-1), atorvastatin group (2.5 mg·kg^-1·d^-1), and aspirin group (12.5 mg·kg^-1·d^-1). The rabbits in normal group was fed with common diet for 12 weeks, and the rabbits in model group were fed with high-fat diet for 12 weeks to establish atherosclerosis model. The rabbits in the rest groups were treated with the corresponding drugs, at the same time to give high-fat diet. Fasting for 12 h after the last treatment, whole blood was collected to perform the blood routine test, and to measure serum and plasma levels of lipids, platelet factor 4 (PF4) and soluble CD62P (sCD62P). Flow cytometry was used to analyze platelet calcium ion concentration. Electron microscopy was used for platelet superfine observations, and light microscopy for observing the pathological changes. RESULTS: Compared with normal group, the levels of triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), platelet counts, and mean platelet volume in model group were significantly elevated, and the levels of PF4, sCD62P and calcium were also significantly increased (P < 0.05). Compared with model group, except aspirin group, the levels of TG, TC and LDL-C in high, medium and low doses of Tongxinluo groups and atorvastatin group were effectively decreased. The platelet counts and mean platelet volume in all treatment groups were markedly decreased, and the serum levels of PF4, sCD62P and Ca²⁺ in platelet (P < 0.05) were reduced. In electron microscopic observation, the shape of platelet was regular and organelles distributed uniform in normal group. However, in model group, the shape of platelet was irregular, pseudopodia forming was obviously observed, and α particles and dense granules decreased, indicating that the platelet was activated. To a different extent, the platelet shape, increase in the number of α particles and dense granules were improved in treatment groups and the damage of the cytoplasm was attenuated. Through histopathological observation, the intimal was smooth and complete in normal group. In the model group, the intimal thickness markedly increased, foam cell aggregated, and plaque was formed. Compared with model group, the intimal thickening and the number of foam cells were significantly decreased, and plaque formation was not obvious in atorvastatin group and high dose of Tongxinluo group. The pathological damages in the other treatment groups were alleviated in different degrees. CONCLUSION: Tongxinluo significantly inhibits the activation of platelets in the process of atherosclerosis, and has important clinical value to delay the atherosclerotic thrombosis.     

Effect of fraction F of naja naja atra venom on protein tyrosine phosphorylation in platelet activation

AIM: To observe the mechanism of intracellular signal transduction that fraction F of naja naja atra venom inhibits platelet aggregation. METHODS: Tests were divided into six groups: (1) blank group; (2) control group and (3)-(6) ADP plus fraction F group (doses of fraction F were 100, 30, 10, 3 mg/L, respectively). Protein tyrosine phosphorylation in platelets was assayed by Western blotting and platelet aggregation was assayed by nephelometer. RESULTS: Fraction F significantly inhibited molecular masses (MW) 76, 66 and 37.5 kD protein tyrosine phosphorylation in platelet that induced by ADP in a dose-dependent manner, in which 30 and 100 mg/L dose group showed obviously different effects when compared to control group (P<0.05). Inhibition of platelet aggregation was positive correlated with protein tyrosine phosphorylation in platelets （r=0.9367, P<0.01）. CONCLUSIONS: Fraction F of naja naja atra venom affected intracellular signal transduction pathway in platelets by inhibiting MW 76, 66 and 37.5 kD protein tyrosine phosphorylation. The result suggests that this effect may be one of the anti-thrombus mechanisms of fraction F.     

Influence of Nao-xue-bao on blood coagulation and platelet aggregation in rats

AIM and METHODS:To study the effect of Nao-xue-bao at three different doses on blood coagulation,platelet aggregation by observing the changes in activated partial thromboplastin time (APTT), prothrombin time (PT), antithrombin-Ⅲ(AT-III), fibrinogen(Fng), plasminogen(Plg) and platelet aggregation(PAG). RESULTS:Compared with thrombosis group, the rats treated with Naoxuebao showed that the plasma APTT,PT were longer, and the activity of AT-III was increased. The content of Fng was reduced, TT was longer, there was a negative correlation between Fng and TT. Furthermore PAG-1, PAG-5 and PAG-M were reduced. CONCLUSION: Nao-xue-bao could inhibit thrombosis in different keys of blood coagulation.     

Effects of cimetidine on platelet function and thrombosis

AIM:To observe the effects of cimetidine(Cim) on platelet function and thrombosis. METHODS:After incubated with Cimin vitro, rat platelets were activated with ADP or thrombin. The platelet aggregation, platelet malondialdehyde(MDA) formation, platelet intracellular free calcium( [Ca²⁺]_i), and thromboxane B₂ (TXB₂) were measured. The effects of Cim on electric-induced thrombosis in rat carotid artery were examined. RESULTS:Cim potentiated ADP induced platelet aggregation, increased the thrombin induced [Ca²⁺]_i and MDA formation, decreased TXB₂. Also, Cim shortened the duration of electric-stimulated occlution time in rat carotid artery. CONCLUSION:Cim increased platelet function and accelerated thrombosis.     

Antiplatelet aggregation of naringenin via cyclic nucleotide signaling:in vitro studies

AIM:To investigate effect of naringenin on ADP-induced platelet aggregation and its possible mechanism.METHODS:The levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were measured in the platelets with ADP stimulation using ELISA in the presence or absence of different concentrations of naringenin.The effect of naringenin at different concentrations on the change of phosphodiesterase (PDE) activity was measured by high efficiency liquid chromatography.The effects of naringenin at different concentrations on phosphorylation of vasodilator-stimulated phosphoprotein (VASP) at positions Ser157 and Ser239 in washed platelets with ADP stimulation were analyzed by Western blot.The phosphorylation of VASP at Ser239 was also analyzed in the presence of protein kinase A (PKA),protein kinase G (PKG),or protein kinase C (PKC) inhibitors before incubation with naringenin.The platelet aggregation was measured in the presence of PKA or PKG inhibitors before incubation with naringenin.RESULTS:Naringenin elevated cGMP levels significantly but not cAMP levels in the platelets with ADP stimulation in a dose-dependent manner.Naringenin inhibited PDE activity.Naringenin increased the phosphorylation of VASP at Ser239 in a dose-dependent manner in the platelets with ADP stimulation but only modest changes in the phosphorylation at position Ser157.The phosphorylation level of VASP at Ser239 position was inhibited when the platelets were treated with PKA inhibitor before incubation with naringenin.Incubation of platelets with neither PKG nor PKC inhibitors before treatment with naringenin affect the phosphorylation of VASP at Ser239.Pretreatment with PKA inhibitor but not PKG inhibitor significantly reversed the antiplatelet aggregation by naringenin in ADP-stimulated platelets.CONCLUSION:Naringenin may inhibit platelet activation through the elevation of cGMP-and PKA-mediated VASP phosphorylation.     

Effects of the juice of Fructus Hippophae (JFH) on thrombocytopenia induced by cyclophosphamide in rats

AIM:To investigate the effects of the juice of fructus hippophae(JFH) on thrombocytopenia in rats.METHODS:Forty-eight wistar rats were divided into control group, model group, Yixuesheng-Jiaonang (YSJN) group and JFH group. Rats were injected intraperitoneally with cyclophosphamide (CTX, 30 mg/kg) or saline once a day for 3 days. And then, Saline, YSJN or JFH was administered (ig) once a day for 11 days. On the second, fouth, sixth and eighth day, the thrombocyte were counted, the mean platelet volume (MPV) and PDW were examined. On the eighth day, the cAMP, cGMP in platelets and platelet aggregation function were also examined.RESULTS:JFH could shorten the time of blood coagulation, increase the count of platelet, and enhance the platelet aggregation function. The experiment also showed that the JFH could decrease cGMP content in platelet.CONCLUSION:JFH could enhance blood coagulation and quality of platelet and prevent thrombocytopenia induced by cyclophosphamide in rats.     

Effect of nitric oxide on adiponectin-induced inhibition of platelet aggregation in hyperlipidemia rats

AIM: To investigate the mechanism that adiponectin inhibits platelet aggregation via nitric oxide (NO) signaling pathway. METHODS: Adult rats were fed with normal or high-fat diet for 14 weeks. Their platelets were immediately isolated and treated with or without recombinant full-length adiponectin (rAPN). The platelet aggregation, NO and superoxide production, endothelial nitric oxide synthase (eNOS)/inducible NOS (iNOS) expression, and antioxidant capacity were determined. RESULTS: Treatment with rAPN inhibited platelet aggregation induced by hyperlipidemia (P<0.05). Interestingly, total NO, a crucial molecule depressing platelet aggregate and thrombus formation, was significantly reduced, rather than increased in rAPN-treated platelets. Treatment with rAPN significantly decreased superoxide production by 62% (P<0.05) and increased antioxidant capacity by 38% (P<0.05) in hyperlipidemic platelets. Importantly, hyperlipidemia-induced reduction of eNOS phosphorylation and increase in iNOS expression were markedly reversed by rAPN treatment (P<0.05 and P<0.01, respectively). CONCLUSION: Adiponectin is an adipokine that inhibits platelet aggregation by enhancing eNOS activation and attenuating oxidative/nitrative stress including blockage of iNOS expression and superoxide production.     

Role of ERK5 in platelet activation in vitro and arterial thrombosis in vivo

AIM: To investigate the role of extracellular signal-regulated kinase 5 (ERK5) in platelet aggregation in vitro and arterial thrombosis in vivo. METHODS: The expression and phosphorylation levels of ERK5 in human platelet were detected by Western blot. The effects of ERK5 selective inhibitor XMD8-92 on platelet aggregation and dense granule secretion were detected by Chrono-Log aggregometer. The effect of ERK5 on in vivo thrombosis was analyzed using an FeCl₃ artery thrombosis model. The effects of XMD8-92 on protein kinase B (PKB/Akt) and phosphatase and tensin homolog deleted on chromosome ten (PTEN) phosphorylation levels were determined by Western blot. RESULTS: ERK5 was stably expressed in human platelets and its phosphorylation level increased significantly after platelet activation (P<0.05). XMD8-92, a selective inhibitor of ERK5, inhibited platelet aggregation and dense granule secretion in response to several platelet stimulators (P<0.05). The results of Western blot showed that XMD8-92 inhibited Akt phosphorylation level by down-regulating PTEN Ser370 phosphorylation and enhancing PTEN activity. The pathway was further confirmed using platelet specific PTEN deficiency mice. The first occlusion time was obviously extended in the mice intravenously given XMD8-92 in the FeCl₃-induced carotid artery injury model. CONCLUSION: ERK5 plays a role in platelet activation and arterial thrombosis by influencing PTEN and Akt phosphorylation.     

Effect of polymorphonuclear leukocytes on washed platelet aggregation

AIM:To investigate the effect of non-activated or activated polymorphonuclear leukocytes(PMN) on washed platelet aggregation. METHODS:Born's method was used to determine platelet aggregation.RESULTS:non-activated PMN (5×10⁹ cells/L) significantly suppressed washed platelet aggregation induced by ADP or arachidonic acid. Aspirin enhanced this inhibition. N-formyl-methiongl-leucy-phenylalanine (fMLP)-or platelet-activating factor (PAF)-stimulated PMN strongly induced platelet aggregation, and the induction effect of PMN suspension was more active than that of PMN supernatant. Aspirin had no significant inhibitory effect on platelet aggregation induced by fMLP-or PAF-activated PMN. CONCLUSIONS:Different conditions of PMN (activated or non-activated) had the nearly opposite action on normal platelet reactivity. Briefly, non-activated-PMN inhibited platelet reactivity, whereas activated PMN stimulated it.