Platelets Activation in Patients Undergoing PTCA and Their Responsiveness After in vitro Stimulation

CD36+/CD61+ Microparticles Correlate with the Risk of Percutaneous Cardiac Interventions in Coronary Artery Disease Patients and the Effects of Ticagrelor

PURPOSE

The CD36 scavenger receptor is a mediator of both atherogenesis and thrombosis. We aimed to investigate the prognostic value of CD36+ microparticles (MPs) released from platelets for cardiovascular event presentation in coronary artery disease (CAD) patients and the effects of different antiplatelet drugs on MPs.

METHODS

A total of 101 aspirin-treated CAD patients, who were planned to undergo coronary angiography (CAG), were randomized to either a standard clopidogrel regimen or ticagrelor treatment. Total Annexin V-(AV)+ MPs, CD61+/AV+ MPs, and CD36+/CD61+/AV+ MPs were quantified by flow cytometry at baseline, before and immediately after the operation. The ADP-induced platelet inhibition rate was measured by thromboelastogram (TEG) examination 1 h before the operation.

RESULTS

The baseline levels of CD36+/CD61+/AV+ MPs were significantly increased in percutaneous coronary intervention (PCI) patients (n = 52) compared to no-PCI patients (n = 49) (p < 0.05). A ROC-curve clustered model for CD36+/CD61+/AV+ MPs at baseline predicted an increased risk of PCI [p = 0.009, AUC = 0.761 (95%CI: 0.601 to 0.922)]. Moreover, TEG examination showed that the preoperative proportion of CD36+/CD61+/AV+ MPs was significantly negatively correlated with R time and K time (r = - 0.236, p = 00.026; r = - 0.288, p = 0.006), and positively correlated with MA_ADP (r = 0.226, p = 0.045). Subgroup analysis of PCI group showed that the platelet inhibition rate of ticagrelor was significantly higher (66.05% ± 28.76% vs.31.01% ± 27.33%, p < 0.001), and the number of AV+ MPs, CD61+/AV+ MPs, and CD36+/CD61+/AV+ MPs before the operation was significantly lower than clopidogrel (p < 0.05, all).

CONCLUSION

The high levels of CD36+ MPs derived from activated platelets are related to an increased risk of PCI in CAD patients. Ticagrelor significantly reduced the number of CD61+/AV+ MPs and CD36+/CD61+/AV+ MPs. This trial registration number is ChiCTR1800014908 and the date of registration is 2018.05.01.

Pharmacological control of platelet-leukocyte interactions by the human anti-P-selectin antibody inclacumab--preclinical and clinical studies

BACKGROUND AND OBJECTIVE

Elevated levels of platelet-leukocyte aggregates (PLAs) have been reported in several cardiovascular diseases and suggested to contribute to disease pathology. Our aim was to characterize the effects of inclacumab, a novel human anti-P-selectin antibody, on the interactions between leukocytes and platelets in preclinical and clinical studies.

EXPERIMENTAL APPROACHES

Dual-label flow cytometry was used to detect the effect of inclacumab on agonist-induced platelet-leukocyte/platelet-monocyte aggregates in cynomolgus monkeys and humans, following ex vivo and in vivo administration. Platelet-dependent leukocyte activation and leukocyte adhesion to a platelet monolayer were also investigated after ex vivo administration of inclacumab to human blood.

RESULTS

Treatment of cynomolgus monkeys with inclacumab profoundly inhibited thrombin receptor-activating peptide (TRAP) or adenosine diphosphate (ADP)-induced PLAs with an IC50 (<2 μg/mL) similar to the in vitro spiking experiments. Maximal inhibition of PLAs persisted for ≥28 days following single dose of inclacumab. In human blood, inclacumab was about 2-fold more potent in inhibiting TRAP-induced PLAs (IC50: 0.7 μg/mL) compared to monkeys. PLA formation was suppressed independently of the inducing platelet agonist. Inclacumab also inhibited the activation of the leukocyte integrin Mac-1 and leukocyte adhesion to a platelet monolayer under flow conditions. In clinical studies, inclacumab inhibited TRAP-induced PLA formation in a dose-dependent manner following single and multiple dose administration to healthy volunteers. It also reduced elevated circulating PLA levels in patients with peripheral arterial disease.

CONCLUSION

By inhibiting platelet-leukocyte interactions, demonstrated in multiple preclinical and clinical studies, inclacumab may provide an effective treatment for cardiovascular diseases.

Improved identification of endothelial erosion by simultaneous detection of endothelial cells (CD31/CD34) and platelets (CD42b)

Loss of endothelial cells (ECs) with ensuing exposure of thrombogenic subendothelial surface is a common cause of thromboembolic complications in atherosclerotic arteries. Thus, endothelial denudation has emerged as a major contributor to the pathogenesis of atherosclerosis and its complications. Despite ongoing efforts in elucidating the pathogenesis of endothelial erosions in human atherosclerotic arteries, the mechanisms of erosion have remained enigmatic, partly due to lack of well-established methods for its identification. Here the authors point out plausible pitfalls in the current methodology and provide an improved immunohistochemical method for identifying endothelial erosion; i.e., immunofluorescence double staining with antibodies against CD42b and CD31/CD34. This method enables reliable detection of ECs and platelets in the same staining by allowing detection of "pseudoendothelium" caused by CD31 staining of a thin platelet layer covering sites of endothelial erosion. As erosion with a luminal platelet thrombus is likely to represent an in vivo erosion, and erosion without platelets an ex vivo artefact, the method makes it possible to exclude artefactual erosions resulting from sample processing. The novel immunostaining protocol presented here allows more reliable detection of endothelial erosions and so may facilitate studies on the mechanisms involved in the pathogenesis of plaque erosion and acute coronary syndromes.