Postprocedural Antiplatelet Treatment after Emergent Carotid Stenting in Tandem Lesions Stroke: Impact on Stent Patency beyond Day 1.

BACKGROUND AND PURPOSE: Postprocedural dual-antiplatelet therapy is frequently withheld after emergent carotid stent placement during stroke thrombectomy. We aimed to assess whether antiplatelet regimen variations increase the risk of stent thrombosis beyond postprocedural day 1. MATERIALS AND METHODS: Retrospective review was undertaken of all consecutive thrombectomies for acute stroke with tandem lesions in the anterior circulation performed in a single comprehensive stroke center between January 9, 2011 and March 30, 2020. Patients were included if carotid stent patency was confirmed at day 1 postprocedure. The group of patients with continuous dual-antiplatelet therapy from day 1 was compared with the group of patients with absent/discontinued dual-antiplatelet therapy. RESULTS: Of a total of 109 tandem lesion thrombectomies, 96 patients had patent carotid stents at the end of the procedure. The early postprocedural stent thrombosis rate during the first 24 hours was 14/96 (14.5%). Of 82 patients with patent stents at day 1, in 28 (34.1%), dual-antiplatelet therapy was either not initiated at day 1 or was discontinued thereafter. After exclusion of cases without further controls of stent patency, there was no significant difference in the rate of subacute/late stent thrombosis between the 2 groups: 1/50 (2%) in patients with continuous dual-antiplatelet therapy versus 0/22 (0%) in patients with absent/discontinued dual-antiplatelet therapy (P = 1.000). In total, we observed 88 patient days without any antiplatelet treatment and 471 patient days with single antiplatelet treatment. CONCLUSIONS: Discontinuation of dual-antiplatelet therapy was not associated with an increased risk of stent thrombosis beyond postprocedural day 1. Further studies are warranted to better assess the additional benefit and optimal duration of dual-antiplatelet therapy after tandem lesion stroke thrombectomy.

ß-arrestin-1 participates in thrombosis and regulates integrin aIIbß3 signalling without affecting P2Y receptors desensitisation and function.

ß-arrestin-1 (ß-arr1) and ß-arrestin-2 (ß-arr2) are cytosolic proteins well-known to participate in G protein-coupled receptor desensitisation and signalling. We used genetically-inactivated mice to evaluate the role of ß-arr1 or ß-arr2 in platelet function, P2Y receptor desensitisation, haemostasis and thrombosis. Platelet aggregation, soluble fibrinogen binding and P-selectin exposure induced by various agonists were near normal in ß-arr1-/- and ß-arr2-/- platelets. In addition, deficiency in ß-arr1 or ß-arr2 was not critical for P2Y receptors desensitisation. A functional redundancy between ß-arr1 and ß-arr2 may explain these unchanged platelet responses. Interestingly, ß-arr1-/- but not ß-arr2-/- mice were protected against laser- and FeCl3-induced thrombosis. The tail bleeding times, number of rebleeds and volume of blood loss were unchanged in ß-arr1-/- and ß-arr2-/- mice, suggesting no defect in haemostasis. ß-arr1-/- platelet activation upon adhesion to immobilised fibrinogen was inhibited, as attested by a 37 ± 5% (n = 3, p<0.0001) decrease in filopodia extension, suggesting defective signalling through integrin αIIbß3. ß-arr1 appeared to be located downstream of Src family kinases and to regulate αIIbß3 signalling by increasing Akt phosphorylation. Overall, this study supports a role for ß-arr1 in promoting thrombus formation, in part through its participation in αIIbß3 signalling, and no role of ß-arr1 and ß-arr2 in agonist-induced platelet activation and P2Y receptors desensitisation.

Mechanisms underlying FeCl3-induced arterial thrombosis.

BACKGROUND: The FeCl(3)-induced vascular injury model is widely used to study thrombogenesis in vivo, but the processes leading to vascular injury and thrombosis are poorly defined. OBJECTIVES: The aim of our study was to better characterize the mechanisms of FeCl(3)-induced vascular injury and thrombus formation, in order to evaluate the pathophysiological relevance of this model. METHODS: FeCl(3) was applied at different concentrations (from 7.5% to 20%) and for different time periods (up to 5 min) to mouse carotid or mesenteric arteries. RESULTS: Under all the conditions tested, ultrastructural analysis revealed that FeCl(3) diffused through the vessel wall, resulting in endothelial cell denudation without exposure of the inner layers. Hence, only the basement membrane components were exposed to circulating blood cells and might have contributed to thrombus formation. Shortly after FeCl(3) application, numerous ferric ion-filled spherical bodies appeared on the endothelial cells. Interestingly, platelets could adhere to these spheres and form aggregates. Immunogold labeling revealed important amounts of tissue factor at their surface, suggesting that these spheres may play a role in thrombin generation. In vitro experiments indicated that FeCl(3) altered the ability of adhesive proteins, including collagen, fibrinogen and von Willebrand factor, to support platelet adhesion. Finally, real-time intravital microscopy showed no protection against thrombosis in GPVI-immunodepleted and ß(1)(-/-) mice, suggesting that GPVI and ß(1) integrins, known to be involved in initial platelet adhesion and activation, do not play a critical role in FeCl(3)-induced thrombus formation. CONCLUSION: This model should be used cautiously, in particular to study the earliest stage of thrombus formation.

Immature myeloid dendritic cells capture and remove activated platelets from preformed aggregates.

BACKGROUND: Immature dendritic cells (DCs) patrol the circulation, where they can uptake antigens. It has been reported that mature monocyte-derived DCs have the ability to interact with an activated platelet monolayer under high shear conditions (1500s(-1) ). OBJECTIVES: In this study, we investigated whether platelets can recruit immature myeloid DCs (CD1c(+) ) directly isolated from blood (BDCs) and if so, which receptors are involved. RESULTS: Using flow cytometry and electron microscopy, we showed that BDCs interact with activated but not resting platelets in suspension. Interaction was also observed after perfusing BDCs under low flow conditions (150 s(-1) ) through collagen-coated microcapillaries in which platelets had adhered and formed aggregates. No such interaction could be detected at higher shear rates. Whereas initial transient attachment required the exposure of P-selectin on activated platelets and PSGL-1 on BDCs, subsequent stationary adhesion was dependent on α(IIb) ß(3) and α(M) ß(2) integrins on platelets and BDCs, respectively. Moreover, during their transient interaction, BDCs preferentially removed platelets located at the outer margin of the thrombus in a P-selectin- and integrin-dependent manner. CONCLUSION: This study provides evidence for an interaction between activated platelets and immature myeloid DCs only under low shear conditions. This could be of importance for BDC maturation and antigen uptake during normal hemostasis or in the context of atherothrombosis at sites of reduced blood flow.

Identification of five novel 14-3-3 isoforms interacting with the GPIb-IX complex in platelets.

BACKGROUND: Binding of von Willebrand factor to the platelet glycoprotein (GP)Ib-IX complex initiates a signaling cascade leading to integrin alpha(IIb)beta(3) activation, a key process in hemostasis and thrombosis. Interaction of 14-3-3zeta with the intracytoplasmic domain of GPIb appears to be a major effector of this activation pathway. OBJECTIVE: The aim of our study was to determine whether other members of the 14-3-3 family bind to GPIb-IX. RESULTS: In this study, western blot analyses showed that platelets also contain the 14-3-3beta, 14-3-3gamma, 14-3-3epsilon, 14-3-3eta and 14-3-3theta isoforms, but lack 14-3-3sigma. Coimmunoprecipitation studies in platelets and CHO transfectants demonstrated that all six 14-3-3 isoforms expressed in platelets, including, as previously reported, 14-3-3zeta, bind to GPIb-IX. In addition, their interaction was found to critically require the same GPIbalpha domains (580-590 and 605-610) already identified as essential for 14-3-3zeta binding, in agreement with the conservation of the sequence of the I-helix among these different isoforms. Pull-down experiments indicated that all six 14-3-3 isoforms present in platelets bind to GPIbbeta. In contrast, deletion or mutation of the GPIbbeta intracytoplasmic tail did not affect the interaction of GPIb-IX with the 14-3-3 isoforms, questioning the importance of this domain. CONCLUSIONS: Our study suggests that, to inhibit GPIb-induced integrin alpha(IIb)beta(3) activation, a more appropriate strategy than inhibiting individual 14-3-3 isoforms would be to target the 14-3-3-binding motif on GPIb or, alternatively, the conserved 14-3-3 I-helix.

Urinary morbidity after 125I brachytherapy of the prostate.

OBJECTIVE: To assess urinary morbidity within the first 6 months after transperineal prostate brachytherapy (TPBT) with 125I for localized prostate adenocarcinoma. PATIENTS AND METHODS: Between September 2000 and July 2001, 50 consecutive patients with favourable early-stage prostate cancer were treated with TPBT. Clinical and objective investigations, including uroflowmetry and postvoid residual urine measurements, were evaluated for short-term urinary morbidity; predictive factors were also sought. RESULTS: Thirty-eight (76%) patients developed urinary disorders, but severe urinary complications were exceptional. The International Prostate Symptom Score (IPSS) changed significantly during the first and third month after implantation and then improved during the sixth month. Concomitantly, the maximum and the average urinary flow rate deteriorated significantly. The variations in postvoid residual were less significant. An initial IPSS of > 8 and previous alpha-blocker treatment were identified as significant predictive factors of urinary morbidity, as were the TPBT dose received by 90% of the target volume and by 30% of the urethra, and the volume of prostate receiving 144 Gy. CONCLUSION: Urinary morbidity after TPBT is frequent but rarely exceptionally severe; patients must therefore be given full information. Patients with a higher initial IPSS or having had previous alpha-blocker treatment, with their associated dosimetric factors, are at greater risk of these urinary morbidity.