Possible existence of platelet activation before the onset of cerebral infarction

Mean Platelet Volume is a Prognostic Marker in Acute Ischemic Stroke Patients Treated with Intravenous Thrombolysis

BACKGROUND AND OBJECTIVES

There is conflicting data regarding the association between platelet parameters and prognosis of stroke patients treated with intravenous thrombolysis. We aimed to analyze this association in a cohort of patients treated with rtPA.

MATERIAL AND METHODS

Retrospective, observational study in adult ischemic stroke patients treated with rtPA between January 2015 and February 2017. Demographic and clinical characteristics, stroke severity (NIHSS), etiology (TOAST), mean platelet volume (MPV), platelet count (PC), platelet distribution width (PDW) and functional outcome (mRS) at discharge and 90 days were recorded. The association between platelet parameters and unfavorable prognosis (mRS 3-6) was tested using non-parametric tests and logistic regression analysis.

RESULTS

267 patients were included, 134 (50.2%) females, with a median (IQR) age of 74 years (64-82). The median admission NIHSS was 14 (8-19) and the most frequent etiology was cardioembolism (n = 115, 43.1%). At discharge, 170 (63.7%) patients had mRS 3-6. MPV values were higher in patients with mRS 3-6 (median 8.2fL versus 7.8fL, p = 0.013). This association remained significant (OR = 1.36, 95% CI 1.003-1.832, p = 0.048) after adjustment for variables associated with prognosis. There were no significant associations between other platelet parameters and prognosis. There was a trend to unfavorable prognosis at 90 days in patients with higher MPV. Regarding the association between platelet parameters and hemorrhagic transformation, higher PDW was associated with more severe hemorrhagic transformation (PH1/PH2).

CONCLUSIONS

Higher MPV values were associated with unfavorable prognosis at discharge in patients treated with intravenous thrombolysis. Future studies should address its added value in stroke prediction models.

Neuro-Immune Hemostasis: Homeostasis and Diseases in the Central Nervous System

Coagulation and the immune system interact in several physiological and pathological conditions, including tissue repair, host defense, and homeostatic maintenance. This network plays a key role in diseases of the central nervous system (CNS) by involving several cells (CNS resident cells, platelets, endothelium, and leukocytes) and molecular pathways (protease activity, complement factors, platelet granule content). Endothelial damage prompts platelet activation and the coagulation cascade as the first physiological step to support the rescue of damaged tissues, a flawed rescuing system ultimately producing neuroinflammation. Leukocytes, platelets, and endothelial cells are sensitive to the damage and indeed can release or respond to chemokines and cytokines (platelet factor 4, CXCL4, TNF, interleukins), and growth factors (including platelet-derived growth factor, vascular endothelial growth factor, and brain-derived neurotrophic factor) with platelet activation, change in capillary permeability, migration or differentiation of leukocytes. Thrombin, plasmin, activated complement factors and matrix metalloproteinase-1 (MMP-1), furthermore, activate intracellular transduction through complement or protease-activated receptors. Impairment of the neuro-immune hemostasis network induces acute or chronic CNS pathologies related to the neurovascular unit, either directly or by the systemic activation of its main steps. Neurons, glial cells (astrocytes and microglia) and the extracellular matrix play a crucial function in a “tetrapartite” synaptic model. Taking into account the neurovascular unit, in this review we thoroughly analyzed the influence of neuro-immune hemostasis on these five elements acting as a functional unit (“pentapartite” synapse) in the adaptive and maladaptive plasticity and discuss the relevance of these events in inflammatory, cerebrovascular, Alzheimer, neoplastic and psychiatric diseases. Finally, based on the solid reviewed data, we hypothesize a model of neuro-immune hemostatic network based on protein–protein interactions. In addition, we propose that, to better understand and favor the maintenance of adaptive plasticity, it would be useful to construct predictive molecular models, able to enlighten the regulating logic of the complex molecular network, which belongs to different cellular domains. A modeling approach would help to define how nodes of the network interact with basic cellular functions, such as mitochondrial metabolism, autophagy or apoptosis. It is expected that dynamic systems biology models might help to elucidate the fine structure of molecular events generated by blood coagulation and neuro-immune responses in several CNS diseases, thereby opening the way to more effective treatments.

Pulmonary platelet accumulation induced by catecholamines: Its involvement in lipopolysaccharide-induced anaphylaxis-like shock

Intravenously injected lipopolysaccharides (LPS) rapidly induce pulmonary platelet accumulation (PPA) and anaphylaxis-like shock (ALS) in mice. Macrophages reportedly release catecholamines rapidly upon stimulation with LPS. Here, we examined the involvement of macrophage-derived catecholamines in LPS-induced PPA and ALS. A catecholamine or Klebsiella O3 (KO3) LPS was intravenously injected into mice, with 5-hydroxytryptamine in the lung being measured as a platelet marker. The tested catecholamines induced PPA, leading to shock. Their minimum shock-inducing doses were at the nmol/kg level. The effects of epinephrine and norepinephrine were inhibited by prazosin (α1 antagonist) and by yohimbine (α2 antagonist), while dopamine's were inhibited only by prazosin. Use of synthetic adrenergic α1- and/or α2-agonists, platelet- or macrophage-depleted mice, a complement C5 inhibitor and C5-deficient mice revealed that (a) α2-receptor-mediated PPA and shock depend on both macrophages and complements, while α1-receptor-mediated PPA and shock depend on neither macrophages nor complements, (b) the PPA and ALS induced by KO3-LPS depend on α1- and α2-receptors, macrophages, and complements, and (c) KO3-LPS-induced PPA is preceded by catecholamines decreasing in serum. Together, these results suggest the following. (i) Catecholamines may stimulate macrophages and release complement C5 via α2-receptors. (ii) Macrophage-derived catecholamines may mediate LPS-induced PPA and ALS. (iii) Moderate PPA may serve as a defense mechanism to remove excess catecholamines from the circulation by promoting their rapid uptake, thus preventing excessive systemic effects. (iv) The present findings might provide an insight into possible future pharmacological strategies against such diseases as shock and acute respiratory distress syndrome.

Platelets and Inflammatory Parameters Do Not Affect Long-Term Survival after Acute Stroke

RATIONALE

According to literature, the inflammatory response and platelets are associated with coronary heart disease mortality. In this study, we examine if similar relationships exist after acute cerebral infarctions.

DESIGN

Between 2005 and 2007, individuals (n = 61) hospitalized with acute stroke were investigated 2.1 ± .3 (SD) days after hospital admission. After 9.3 ± .7 (SD) years, 29 patients (age 79 ± 8 [SD]; 12 women) had died. They were compared with survivors (age 69 ± 9 [SD]; 9 women) with respect to inflammatory parameters and platelet features such as activity and reactivity.

RESULTS AND CONCLUSION

Inflammation and platelets at the acute event do not forecast long-term survival of stroke sufferers.

Leukocyte-platelet aggregates-a phenotypic characterization of different stages of peripheral arterial disease

The formation of monocyte-platelet aggregates and neutrophil-platelet aggregates (MPA and NPA, respectively) is influenced by inflammation, but also might contribute to an exacerbation of inflammatory responses in atherosclerotic plaque. The purpose of this study was to analyze MPA and NPA proportions in regard to different stages of peripheral arterial disease (PAD). Forty-five patients with intermittent claudication (IC) (3 groups: Rutherford (R)-1, R-2, and R-3; each n = 15), 20 patients with critical limb ischemia (CLI) (Rutherford 5 (40%) and 6 (60%)), and 20 healthy controls were studied. Analyses of monocyte (Mon) subpopulations (CD14++CD16- (classical) Mon1, CD14++CD16+ (intermediate) Mon2, CD14+CD16++ (non-classical) Mon3), MPA, and NPA was performed from whole blood by flow cytometry. Controls showed an increased proportion of the Mon1 subpopulation (p < 0.001), whereas CLI patients showed a significant increase of the Mon2 subpopulation compared to controls, R-1, or R-2 patients (p < 0.0001). For the Mon3 subpopulation, CLI and R-3 patients showed an increased proportion (p < 0.05). MPA formation with the proinflammatory Mon2 and Mon3 subpopulations was increased in CLI patients (both p < 0.01). Similarly, NPA was significantly increased in CLI patients (p < 0.05). Serological markers of inflammation and procoagulation (fibrinogen [r = 0.459, p < 0.001], soluble triggering receptor expressed on myeloid cells (sTREM-1) [r = 0.237, p < 0.05] and P-Selectin [r = 0.225, p < 0.05]) correlated directly with MPA formation on the Mon2 subpopulation. We found an association of inflammatory and procoagulatory markers with increased formation of MPA on the Mon2 subpopulation. Since R-3 patients also had significantly increased MPA, one can speculate that the inflammatory burden might promote an aggravation of the disease.

Circulating levels of platelet α-granule cytokines in trauma patients

OBJECTIVE AND DESIGN

To elucidate whether platelets differentiate cytokine release following trauma, we prospectively measured three major platelet-derived cytokines in 213 trauma patients on hospital arrival.

METHODS

We measured plasma levels of the anti-inflammatory β-thromboglobulins (βTGs), transforming growth factor-β1 (TGFβ1) and the pro-inflammatory platelet factor 4 (PF4) cytokines. We also measured soluble glycoprotein VI (sGPVI), procoagulant platelet microparticles (PMPs) and white blood cell (WBC) counts, and evaluated in vitro platelet function in primary and secondary haemostasis by aggregometry and thromboelastometry, respectively. We evaluated associations of each cytokine by multivariate regression including injury severity score (ISS), WBC counts, sGPVI and platelet counts as explanatory variables.

RESULTS

Severely injured patients (ISS > 15) had higher levels of βTGs and TGFβ1 (both p < 0.01) but lower levels of PF4 (p = 0.02). GPVI and PMPs levels correlated with TGFβ1 and PF4 whereas we found no significant association between cytokine levels and measures of haemostasis. By multivariate regression, a high WBC count was associated with high levels of TGFβ1 (p = 0.01) and βTGs (p < 0.01) but with low levels of PF4 (p = 0.03).

CONCLUSION

Severely injured patients had higher levels of βTGs and TGFβ1 but lower levels of the PF4; a high WBC count predicted this anti-inflammatory profile of platelet cytokines.

Morphology of platelet Golgi apparatus and their significance after acute cerebral infarction

Blood samples were harvested from the antecubital vein of 20 fasting patients with acute cerebral infarction at 1, 7 and 15 days after onset to prepare blood platelet suspension. Fasting antecubital vein blood was collected from an additional 20 normal adults as controls. Under transmission tron microscope, platelet Golgi tubules and vesicles became significantly thickened, enlarged, and irregular after acute cerebral infarction. Alpha granules in platelets significantly reduced in number, especially 1 day after cerebral infarction. Under immunoelectron microscopy, a few alpha granules aggregated around Golgi tubules and vesicles after infarction. These results suggested that platelet Golgi apparatus displayed significant morphological changes, which were possibly associated with enhanced synthetic and secretory functions of activated platelets after acute cerebral infarction. This study used Golgi apparatus blocking agent Brefeldin A to block Golgi apparatus in an aim to study the effects of Golgi apparatus on CD40L expression on the surface of activated platelets. Flow cytometry revealed that CD40L expression on activated platelet surfaces decreased significantly when Golgi apparatus was blocked, which indicated that Golgi apparatus participated in the synthesis and transport of CD40L to the platelet surface.

Proteomic analysis reveals platelet factor 4 and beta-thromboglobulin as prognostic markers in severe acute respiratory syndrome

Previously, we reported that proteomic fingerprints were present in sera of patients with severe acute respiratory syndrome (SARS), and could separate patients into subgroups with different prognoses. In the present study, we examined the prognostic values of the SARS-associated proteomic features by biostatistical analysis, and deciphered the identities of those with prognostic values. Data of 20 SARS-associated serum proteomic features and ten serological variables from 38 SARS adult patients before treatment were subjected to multivariate logistic regression. Proteomic features of m/z 6634, m/z 7769, m/z 8635, and m/z 8865 were identified as independent prognostic markers. After purification by cation-exchange chromatography and gel electrophoresis, proteomic features of m/z 7769 and m/z 8865 were found to be platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG) by tandem mass spectrometry, respectively. The associations of decreased serum PF4 and increased serum beta-TG levels with poor prognosis were confirmed by Western blot. Previous studies suggest that PF4 and beta-TG are involved in the pathogenesis of acute respiratory distress syndrome (ARDS) in a negative and positive way, respectively. Our results suggest that PF4 and beta-TG may also play similar roles in the development of ARDS in SARS patients.

Thrombopoietin and mean platelet volume in patients with ischemic stroke

OBJECTIVE

The aim of this study was to evaluate mean platelet volume (MPV), thrombopoietin (TPO), and platelet levels in patients with ischemic stroke and compare this with healthy controls.

METHODS

We prospectively studied 50 patients with ischemic stroke and compared them with 37 control participants who have evaluated in internal medicine polyclinic and had no history of cerebrovascular events. All patients were within 24 hours after stroke; MPV and TPO were measured on admission.

RESULTS

Both TPO and MPV values were significantly higher in patients with stroke (P = .00; P = .001).

CONCLUSION

Increased TPO levels may increase both platelet count and platelet size, resulting in more hemostatic tendency, which may contribute to the progression of ischemic stroke.

Platelet activation is caused not by aging but by atherosclerosis

Platelet activation increases with age, although it is still controversial whether it derives from aging per se or from atherosclerosis concomitant with aging. The purpose of this study is to clarify the association between platelet activation and aging or atherosclerosis. We studied the ultrastructure of platelets in the elderly subjects with or without atherosclerosis and healthy young subjects. The platelet shape changes were evaluated by transmission electron microscopy and the contents of peroxidase and fibrinogen were assessed using a scoring system based on cytochemical staining and immunogold marking methods. No significant differences in platelet shape changes and the contents of peroxidase and fibrinogen in platelet were observed between healthy young and nonatherosclerotic elderly subjects, although the frequency of pseudopods increased and the content of peroxidase decreased in atherosclerotic elderly patients. It is suggested that platelet activation is not derived from aging but from atherosclerosis, although it is difficult to separate aging from coexisting atherosclerosis.

The effects of antiplatelet agents on platelet-leukocyte aggregations in patients with acute cerebral infarction

BACKGROUND

Studies have shown that platelet-leukocyte aggregates (PLA) are sensitive to platelet activation which might exist before the onset of cerebral infarction. In this study, we investigated the formation of PLA in patients with cerebral infarction and the effects of antiplatelet agents on PLA.

METHODS

The level of soluble P-selectin, C-reaction protein, platelet aggregation rate and leukocyte-platelet aggregations were measured in 40 patients with acute cerebral infarction and 20 normal controls. The 40 patients were randomly assigned to two treatment groups: aspirin group (n = 20) and clopidogrel group (n = 20). Both groups were monitored for Scandinavian stroke scale (SNSS), soluble P-selectin, serum C-reaction protein, platelet aggregation rate and PLA before and after the treatment. Flow cytometry was used to detect the levels of PLA in the blood.

RESULTS

The percentage of platelet-monocyte aggregates (PMA) in patients with cerebral infarction was significantly increased compared with the controls (P < 0.001), which was positively correlated to soluble P-selectin, C-reaction protein and platelet aggregation rate (P < 0.05). After the treatment, the levels of PMA and platelet aggregation rate were decreased in both groups (P < 0.05). The level of PMA and platelet aggregation rate in the clopidogrel group was significantly lower than that in the aspirin group (P < 0.05).

CONCLUSIONS

PMA are a sensitive biomarker to platelet activation in patients with cerebral infarction. In addition, although both aspirin and clopidogrel lowered the level of PMA, clopidogrel is a more effective treatment than aspirin in inhibiting platelet activation.

Advances in ischemic stroke treatment: neuroprotective and combination therapies

Thrombolysis with intravenous alteplase (recombinant tissue-type plasminogen activator) continues to be the sole recourse for acute ischemic stroke therapy, provided that patients seek treatment preferably within 3 h of stroke onset. The narrow window of efficacy, coupled with the significant risk of hemorrhage and the high mortality rate, preclude the use of alteplase beyond this time frame. Moreover, in part because of safety concerns, only a small percentage (6-15%) of eligible patients is treated with alteplase. Clearly, safer and more effective treatments that focus on improving the shortcomings of the present thrombolysis for stroke need to be identified. Therefore, newer thrombolytics are being developed with the goal of minimizing side effects, while also shortening the time of cerebral reperfusion and extending the therapeutic window of efficacy. Besides thrombolytics, new and potentially useful drugs and devices are also being studied either as monotherapeutic agents or for use in conjunction with alteplase. In animal models of stroke, neuroprotective agents that affect various components of the ischemic injury cascade that results in neurodegeneration have shown promise for the latter. Examples of such agents include spin traps that block oxidative stress, metalloprotease inhibitors that prevent vascular damage, anti-inflammatory drugs that suppress inflammation and transcranial infrared laser irradiation, which promotes recovery of function. Ideally, a successful combination of neuroprotectant (drug or device) and thrombolytic therapy for stroke would minimize the side effects of thrombolysis followed by supplementary neuroprotection thereafter.

Therapeutic effects of hydroxysafflor yellow A on focal cerebral ischemic injury in rats and its primary mechanisms

The therapeutic effects of hydroxysafflor yellow A (HSYA), extracted from Carthamus tinctorius. L, on focal cerebral ischemic injury in rats and its related mechanisms have been investigated. Focal cerebral ischemia in rats were made by inserting a monofilament suture into internal carotid artery to block the origin of the middle cerebral artery and administrated by HSYA via sublingular vein injection in doses of 1.5, 3.0, 6.0 mg kg(-1) at 30 min after the onset of ischemia, in comparison with the potency of nimodipine at a dose of 0.2 mg kg(-1). Then, 24 h later, the evaluation for neurological deficit scores of the rats were recorded and postmortem infarct areas determined by quantitative image analysis. At the end of the experiment, blood samples were taken to determine plasma 6-Keto-PGF1alpha/TXB2 by radioimmunoassays and blood rheological parameters. The effects exerted by HSYA on thrombosis formation by artery vein by-pass method and ADP-induced platelet aggregation in vivo and in vitro were investigated, respectively. The results indicated that more than 30% of the area of ischemic cerebrum was observed in the ischemic model group. HSYA dose-dependently improved the neurological deficit scores and reduced the cerebral infarct area, and HSYA bore a similarity in potency of the therapeutic effects on focal cerebral ischemia to nimodipine. The inhibition rates of thrombosis formation by HSYA at the designated doses were 20.3%, 43.6% and 54.2%, respectively, compared with saline-treated group. Inhibitory activities of HSYA were observed on ADP-induced platelets aggregation in a dose-dependent manner, and the maximum inhibitory aggregation rate of HSYA was 41.8%. HSYA provided a suppressive effect on production of TXA2 without significant effect on plasma PGI2 concentrations. Blood rheological parameters were markedly improved by HSYA, such as whole blood viscosity (from 21.71 +/- 4.77 to 11.61 +/- 0.90 mPa.s), plasma viscosity (from 2.73 +/- 0.53 to 1.42 +/- 0.07 mPa.s), deformability (from 0.66 +/- 0.26 to 0.77 +/- 0.33) and aggregation of erythrocyte (from 3.24 +/- 0.41 to 2.57 +/- 0.30), but no significant effect of HSYA on homatocrit was found (from 51.38 +/- 4.68% to 49.91 +/- 2.32%). HSYA appears to be a good potential agent to treat focal cerebral ischemia, and the underlying mechanisms exerted by HSYA might be involved in its inhibitory effects on thrombosis formation and platelet aggregation as well as its beneficial action on regulation of PGI2/TXA2 and blood rheological changes in rats.

Soluble platelet glycoprotein V is a marker of thrombosis in patients with ischemic stroke

BACKGROUND AND PURPOSE

The diagnosis and management of patients with acute ischemic stroke still lack an informative biochemical test. Soluble glycoprotein V (sGPV) is a new plasmatic marker of thrombosis released from the platelet surface by thrombin. The objective of this prospective study was to compare the levels of sGPV in stroke and control patients.

METHODS

Consecutive patients with acute ischemic stroke (n=159) and controls (n=70) were recruited for sGPV measurement.

RESULTS

Plasmatic levels of sGPV were significantly increased in ischemic stroke compared with control patients (median [interquartile range] 39.4 [31.8 to 52.9] versus 28.1 [24.0 to 37.9] ng/mL; P<0.0001). In multivariate analysis, ischemic stroke was the major determinant of the sGPV increase (odds ratio [95% CI], 5.87 [2.62 to 13.12]; P<0.0001).

CONCLUSIONS

sGPV is a new marker of arterial thrombosis and represents a tool to study the mechanisms involved in ischemic stroke. The increase in plasmatic sGPV observed in stroke patients supports a role of platelets and thrombin in the events leading to ischemic stroke.

Sneddon syndrome with multiple cerebral infarctions 12 years after the onset of livedo vasculitis: a possible involvement of platelet activation

Sneddon syndrome is characterized by livedo reticularis and multiple cerebral infarctions. Skin and central nervous system symptoms usually have a synchronous onset and at times initial symptoms affect one of them, the other lagging several years behind. We here report a patient with Sneddon syndrome who developed multiple cerebral infarctions more than 10 years after the onset of livedo reticularis. While the neurological symptoms were apparent, the patient did not display active skin manifestations. Laboratory findings excluded collagen diseases, antiphospholipid antibody syndrome, and inherited quantitative deficiency of protein C, protein S and antithrombin III. Abnormal findings included extremely elevated levels of beta-thromboglobulin and platelet factor-4 in the blood, although these acute phase markers of thrombosis were examined several years after the onset of cerebral infarctions. Platelet activation may have caused Sneddon syndrome in the present case.