The hemostatic agent ethamsylate enhances P-selectin membrane expression in human platelets and cultured endothelial cells

Ethamsylate possesses antihemorrhagic properties, but whether or not it directly activates blood platelets is unclear. Here we investigated the platelet activation potential of ethamsylate, by measuring membrane P-selectin expression with flow cytometry in human whole blood and also by immunofluorescence imaging of isolated human platelets. Moreover, we measured membrane P-selectin expression in the SV40-transformed aortic rat endothelial cell line (SVAREC) and ¹⁴C-ethamsylate membrane binding and/or uptake in platelets and endothelial cells. Whole blood flow cytometry showed a modest, but statistically significant increase by ethamsylate in the percentage of platelets expressing P-selectin (from 2% to 4–5%, p<0.05). Immunofluorescence showed a sizable (39%) and significant (p<0.01) enhancement of P-selectin expression at the lowest concentration of ethamsylate tested (1 μM), with maximal enhancement of P-selectin expression (75–90%) at 10 μM ethamsylate. Similar results were obtained in SVAREC endothelial cells. ¹⁴C-ethamsylate specifically bound to platelets and endothelial cell membranes, without significant uptake into the cell interior. In conclusion, ethamsylate enhances membrane P-selectin expression in human platelets and in cultured endothelial cells. Ethamsylate specifically binds to some protein receptor in platelet and endothelial cell membranes, receptor which can signal for membrane P-selectin expression. These results support the view that ethamsylate acts on the first step of hemostasis, by improving platelet adhesiveness and restoring capillary resistance.     

Elevated inflammatory parameters are associated with lower platelet density in acute myocardial infarctions with ST-elevation

Objective: Platelets and granulocytes play important roles in coronary disorders. We therefore, investigated platelet and granulocyte alterations in myocardial infarctions (MIs). Patients and study design: A total of 36 individuals having MI with raised ST-segments who were receiving thrombolytic therapy were studied. Sampling was carried out after thrombolysis within 24 h after hospital admission. After 3 to 6 months of recovery, 25 patients were reinvestigated. At the infarction, peak platelet density was determined using a special designed computerised apparatus. In addition, we did counts on platelets, neutrophils and monocytes. Moreover, plasma levels of soluble P-selectin, myeloperoxidase and interleukin 6 were determined to estimate the degree of platelet, neutrophil and monocyte activation, respectively. Peak platelet density was analysed at the MI. All other parameters were determined at the acute event and at recovery. Results: At the MI, compared to the recovery, platelet counts were lower (P<.001). In addition, increased neutrophil counts (P<.001), elevated monocyte counts (P<.001), enhanced myeloperoxidase (P<.001) and interleukin 6 (P<.001) levels were demonstrated. We failed to show elevated soluble P-selectin. Compared to individuals with ST-segment elevations and low platelet density (≤1.058 kg/l), patients having peak platelet densities >1.058 kg/l displayed lower neutrophil counts (P<.01) and decreased interleukin 6 levels (P<.01). Furthermore, we demonstrate that individuals with higher inflammatory response at the MI had higher neutrophil (r=.6; P<.01) and higher monocyte counts (r=.6; P<.001) at recovery. Conclusion: We conclude that MI is associated with an inflammatory response. However, a subgroup of patients having MI with ST-elevations and low peak platelet density was identified. Compared to subjects with higher platelet density, they had more severe inflammatory characteristics. The differences persisted during recovery.     

Serotonin transporter characteristics in lymphocytes and platelets of male aggressive schizophrenia patients compared to non-aggressive schizophrenia patients

A large body of literature indicates that disturbances of central serotonin (5-HT) function play an important role in aggressive behavior. Results from open-label and placebo-controlled trials as well as the reported inverse relationship between 5-HT function and aggression in human subjects, suggest that reduced 5-HT activity is associated with aggressive behavior. The activity of the 5-HT transporter (5-HTT), as determined by [³H]5-HT uptake to blood lymphocytes, was measured in 20 currently aggressive and 20 non-aggressive male schizophrenia patients. In addition, the pharmacodynamic characteristics of platelet 5-HTT were assessed by [³H]citalopram binding.

There were no significant differences in the density (B_max) of platelet [³H]citalopram binding sites between the two groups. Similarly, the dissociation constant (K_d) values were indistinguishable. The maximum uptake velocity (V_max) of [³H]5-HT to fresh lymphocytes and the K_m values of the 5-HT to the transporter were significantly higher in currently aggressive compared to the non-aggressive schizophrenia patients. The association of high V_max values with current aggressive behavior provides further support to the involvement of the 5-HTT in aggressive behavior as well as to the efficacy of 5-HTT blockers in the control of aggression. The role of the various components of the serotonergic system in the pathophysiology and treatment of aggressive behavior in schizophrenia needs to be further evaluated.     

深低温保存血小板临床应用疗效评价

目的 评估深低温保存血小板在临床输注的有效性与安全性。方法 对1，294例输注患者进行深低温保存血小板输注研究。其中各类型白血病326例，再生障碍性贫血167例，恶性肿瘤放疗及化疗及其它原因所致的血小板减少254例，术前、术中、术后输注血小板547例。现察输注前、后1h出血时间，输后伤口停止出血时间、血小板计数、体表瘀斑消散情况、不良反应等各项指标。结果 输注深低温保存的血小板具有升高血小板作用和显著的止血效果，内科输注总有效率89．8％，外科输注总有效率95．1％，无明显副作用发生。结论 深低温保存血小板在内、外科出血患者应用均安全、有效。     

Antithrombotic effects of aspirin and LMWH in a laser-induced model of arterials and venous thrombosis

Antiplatelet drug aspirin and anticoagulant low molecular weight heparin (LMWH) were compared as arterial and venous antithrombotic preparations in the rat experimental model of the laser induced thrombus formation.

A method to induce microthrombi in small mesenteric vessel (15–25 μm) has been developed to investigate antithrombotic drugs and to study platelet reactions. Mesenteric injuries are induced in the vascular system of Wistar rats with an argon laser. The laser beam induced formation of the vessel wall injury with damage of endothelial cells. Thrombus was formed within seconds after laser injury and grew rapidly. The aggregate can be swept away by the flow and a new thrombus was formed again. This embolization began within the minute following the laser flash. Thrombus formation and embolization were repetitive phenoma. Aspirin (100 mg/kg) and LMWH (1 mg/kg) are approximately the same as to decrease the number of emboli detached from the thrombus and the duration of embolization; both in venules and in arterioles.

This results suggest reflexion about the role of platelets in venous thrombosis induced by laser beam.     

Lack of a role for blood platelets in the uptake of 5-hydroxytryptamine by the rabbit heart

Perfused rabbit hearts removed 5-hydroxytryptamine (5-HT) from a perfusion solution of 1.0 × 10^?8 g ml^?1 and at the same time their endogenous 5-HT concentrations increased. Pretreatment of animals with heparin did not affect either the removal of 5-HT from the perfusion fluid or its accumulation in the heart. The proportion of 5-HT removed from the perfusion fluid which was subsequently found in the heart was small in both the heparinised and the non-heparinised groups. The results suggest that platelets trapped within heart tissue are unimportant for cardiac 5-HT uptake.     

Synergistic antithrombotic effect of a combination of NO donor and plasma kallikrein inhibitor

The aim of the present study was to investigate the effect of a NO donor (GSNO) and a plasma kallikrein inhibitor (PKSI-527) alone and in combination on global haemostatic status. A new in vitro test was employed which allows the measurement of both platelet function and spontaneous thrombolysis. Sixteen healthy young and 18 elderly volunteers were enrolled in this study. When GSNO (1 mM) or PKSI-527 (20 microM) was added to native human blood, platelet reactivity was significantly inhibited in both age groups. The combination of GSNO and PKSI-527 had additive inhibitory effect on platelets. Addition of either GSNO or PKSI-527 to blood samples did not significantly affect spontaneous thrombolysis, while added together, spontaneous thrombolysis was significantly enhanced. The thrombolysis enhancing effect was more prominent in elderly subjects. Our present findings suggest that the combination of NO donor and plasma kallikrein inhibitor may have clinical antithrombotic potential.     

Alcohol consumption and platelet activation and aggregation among women and men: the Framingham Offspring Study

BACKGROUND: Alcohol intake has been associated with lower platelet activity; however, few large-scale studies have included women, and to our knowledge, the relationship of alcohol intake with measures of platelet activation has not been studied. METHODS: We performed a cross-sectional analysis of adults free of cardiovascular disease enrolled in the Framingham Offspring Study. Study physicians assessed alcohol consumption with a standardized questionnaire. We measured platelet activation in response to 1 and 5 microm of adenosine diphosphate (ADP) with a P-selectin assay among 1037 participants and platelet aggregability in response to ADP, epinephrine, and collagen among 2013 participants. RESULTS: Alcohol consumption was inversely associated with P-selectin expression in response to 1 microm ADP (p = 0.007) and 5 microm ADP (p = 0.02) among men but not women. Alcohol consumption was also inversely associated with platelet aggregation induced by ADP among both women (p = 0.04) and men (p trend = 0.008) and by epinephrine among men (p = 0.03) CONCLUSIONS: Alcohol consumption is inversely associated with both platelet activation and aggregation, particularly in men. Additional research is needed to determine whether these findings contribute to the contrasting associations of alcohol consumption with risk of thrombotic and hemorrhagic cardiovascular events.