Center for Translational Research on Inflammatory Diseases, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA.
Department of Medicine, Baylor College of Medicine, Houston, Texas, USA.
Microcirculation. 2022 Nov;29(8):e12782. doi: 10.1111/micc.12782. Epub 2022 Sep 22.
Extracellular histones are known mediators of platelet activation, inflammation, and thrombosis. Von Willebrand Factor (vWF) and Toll-like receptor 4 (TLR4) have been implicated in pro-inflammatory and prothrombotic histone responses. The objective of this study was to assess the role of vWF and TLR4 on histone-induced platelet adhesion in vivo.
Intravital microscopy of the mouse cremaster microcirculation, in the presence of extracellular histones or saline control, was conducted in wild-type, vWF-deficient, and TLR4-deficient mice to assess histone-mediated platelet adhesion. Platelet counts following extracellular histone exposure were conducted. Platelets were isolated from vWF-deficient mice and littermates to assess the role of vWF on histone-induced platelet aggregation.
Histones promoted platelet adhesion to cremaster venules in vivo in wild-type animals, as well as in TLR4-deficient mice to a comparable degree. Histones did not lead to increased platelet adhesion in vWF-deficient mice, in contrast to littermate controls. In all genotypes, histones resulted in thrombocytopenia. Histone-induced platelet aggregation ex vivo was similar in vWF-deficient mice and littermate controls.
Histone-induced platelet adhesion to microvessels in vivo is vWF-dependent and TLR4-independent. Platelet-derived vWF was not necessary for histone-induced platelet aggregation ex vivo. These data are consistent with the notion that endothelial vWF, rather than platelet vWF, mediates histone-induced platelet adhesion in vivo.
细胞外组蛋白是已知的血小板激活、炎症和血栓形成的介质。血管性血友病因子 (vWF) 和 Toll 样受体 4 (TLR4) 已被牵涉到促炎和促血栓形成的组蛋白反应中。本研究的目的是评估 vWF 和 TLR4 在体内组蛋白诱导的血小板黏附中的作用。
在存在细胞外组蛋白或生理盐水对照的情况下，通过活体显微镜观察小鼠提睾肌微循环，以评估组蛋白介导的血小板黏附。在暴露于细胞外组蛋白后进行血小板计数。从 vWF 缺陷型小鼠及其同窝仔鼠中分离血小板，以评估 vWF 在组蛋白诱导的血小板聚集中的作用。
组蛋白在野生型动物以及 TLR4 缺陷型小鼠体内促进血小板黏附到提睾肌小静脉，其程度与 TLR4 缺陷型小鼠相当。与同窝仔鼠对照相比，组蛋白并未导致 vWF 缺陷型小鼠的血小板黏附增加。在所有基因型中，组蛋白均导致血小板减少症。体外组蛋白诱导的血小板聚集在 vWF 缺陷型小鼠及其同窝仔鼠中相似。
体内组蛋白诱导的血小板黏附至微血管是 vWF 依赖性且 TLR4 非依赖性的。血小板衍生的 vWF 对于体外组蛋白诱导的血小板聚集并非必需。这些数据与内皮 vWF 而非血小板 vWF 介导体内组蛋白诱导的血小板黏附的观点一致。
