Neutrophils are implicated in the pathogenesis of atherosclerosis but are seldom detected in atherosclerotic plaques. We investigated whether neutrophil-derived microvesicles may influence arterial pathophysiology. Here we report that levels of circulating neutrophil microvesicles are enhanced by exposure to a high fat diet, a known risk factor for atherosclerosis. Neutrophil microvesicles accumulate at disease-prone regions of arteries exposed to disturbed flow patterns, and promote vascular inflammation and atherosclerosis in a murine model. Using cultured endothelial cells exposed to disturbed flow, we demonstrate that neutrophil microvesicles promote inflammatory gene expression by delivering miR-155, enhancing NF-κB activation. Similarly, neutrophil microvesicles increase miR-155 and enhance NF-κB at disease-prone sites of disturbed flow in vivo. Enhancement of atherosclerotic plaque formation and increase in macrophage content by neutrophil microvesicles is dependent on miR-155. We conclude that neutrophils contribute to vascular inflammation and atherogenesis through delivery of microvesicles carrying miR-155 to disease-prone regions.

Platelet hyperaggregation and hypercoagulation are associated with increase of thrombogenic risk, especially in patients with type 2 diabetes (T2D). High activity of P2Y12 receptor is found in T2D patients, exposing such patients to a prothrombotic condition. P2Y12 is a promising target for antiplatelet, but due to P2Y12 receptor constitutive activation, the clinical practical phenomena such as "clopidogrel resistance" are commonly occurring. In this study, we investigate the role of lncRNA on platelet activation. By lncRNA array, we screened thousands of differentially expressed lncRNA in megakaryocytes from T2D patients and confirmed that lncRNA metallothionein 1 pseudogene 3 (MT1P3) was significantly upregulated in megakaryocytes from T2D patients than in healthy controls. And we further investigate the biofunction of MT1P3 on platelet activation and the regulatory mechanism on p2y12. MT1P3 was positively correlated with p2y12 mRNA levels and promoted p2y12 expression by sponging miR-126. Knockdown of MT1P3 by siRNA reduced p2y12 expression, inhibiting platelet activation and aggregation in diabetes animal model. In conclusion, our findings identify MT1P3 as a key regulator in platelet activation by increasing p2y12 expression through sponging miR-126 under T2D condition. These findings may provide a new insight for managing platelet hyperactivity-related diseases.

Thrombocytopenia or chronic depletion of platelets in blood, could create life-threatening conditions in patients who receive aggressive systemic radiation and chemotherapy. Currently there are no approved agents for the rapid treatment of thrombocytopenia. In the present study, we demonstrate that administration of Orientin, a glycosidic flavonoid or dietary administration of Orientin containing Tulsi (Holy Basil) leaves, results in a significant increase in circulating platelets in a clinically relevant mouse model. No noticeable effects were observed on red blood cells, white blood cells or other hematologic parameters in treated animals indicating that Orientin specificity enhances platelet formation. The gene expression and immunophenotyping of bone marrow revealed that Orientin stimulates megakaryopoiesis specific transcriptional program. A significant increase in colony formation in bone marrow cells from Orientin pretreated mice further complemented the effect of Orientin on progenitor cells. The ex-vivo differentiation of irradiated human peripheral blood CD34+ stem cells demonstrated stimulatory effects of Orientin on megakaryocyte erythrocyte progenitors (MEP). The results show that Orientin, a non-toxic readily available natural product can counter platelet imbalances. Thrombocytopenia also develop as a consequence of multiple hematologic malignancies and side effects of treatments. Dietary supplementation of Orientin containing phytochemicals could be effective as countermeasures and viable therapeutics.

Platelet activation requires rapid remodeling of the actin cytoskeleton which is regulated by small GTP-binding proteins. By using the Rac1-specific inhibitor NSC23766, we have recently found that Rac1 is a central component of a signaling pathway that regulates dephosphorylation and activation of the actin-dynamising protein cofilin, dense and α-granule secretion, and subsequent aggregation of thrombin-stimulated washed platelets.
To study whether NSC23766 inhibits stimulus-induced platelet secretion and aggregation in blood.
Human platelet aggregation and ATP-secretion were measured in hirudin-anticoagulated blood and platelet-rich plasma (PRP) by using multiple electrode aggregometry and the Lumi-aggregometer. Platelet P-selectin expression was quantified by flow cytometry.
NSC23766 (300 μM) inhibited TRAP-, collagen-, atherosclerotic plaque-, and ADP-induced platelet aggregation in blood by 95.1%, 93.4%, 92.6%, and 70%, respectively. The IC50 values for inhibition of TRAP-, collagen-, and atherosclerotic plaque-, were 50 ± 18 μM, 64 ± 35 μM, and 50 ± 30 μM NSC23766 (mean ± SD, n = 3-7), respectively. In blood containing RGDS to block integrin αIIbβ3-mediated platelet aggregation, NSC23766 (300 μM) completely inhibited P-selectin expression and reduced ATP-secretion after TRAP and collagen stimulation by 73% and 85%, respectively. In ADP-stimulated PRP, NSC23766 almost completely inhibited P-selectin expression, in contrast to aspirin, which was ineffective. Moreover, NSC23766 (300 μM) decreased plaque-stimulated platelet adhesion/aggregate formation under arterial flow conditions (1500s-1) by 72%.
Rac1-mediated signaling plays a central role in secretion-dependent platelet aggregation in blood stimulated by a wide array of platelet agonists including atherosclerotic plaque. By specifically inhibiting platelet secretion, the pharmacological targeting of Rac1 could be an interesting approach in the development of future antiplatelet drugs.