Center for Thrombosis and Hemostasis (CTH), University Medical Center, Johannes Gutenberg-University Mainz, Mainz, Germany.
Deutsche Klinik für Diagnostik HELIOS Klinik, Wiesbaden, Germany.
FASEB J. 2020 Jul;34(7):9337-9357. doi: 10.1096/fj.201903189R. Epub 2020 May 28.
Thrombin converts fibrinogen to fibrin and activates blood and vascular cells in thrombo-inflammatory diseases. Platelets are amplifiers of thrombin formation when activated by leukocyte- and vascular cell-derived thrombin. CD36 on platelets acts as sensitizer for molecules with damage-associated molecular patterns, thereby increasing platelet reactivity. Here, we investigated the role of CD36 in thrombin-generation on human platelets, including selected patients with advanced chronic kidney disease (CKD). Platelets deficient in CD36 or blocked by anti-CD36 antibody FA6.152 showed impaired thrombin generation triggered by thrombin in calibrated automated thrombography. Using platelets with congenital function defects, blocking antibodies, pharmacological inhibitors, and factor-depleted plasma, CD36-sensitive thrombin generation was dependent on FXI, fibrin, and platelet signaling via GPIbα and SFKs. CD36-deficiency or blocking suppressed thrombin-induced platelet αIIbβ3 activation, granule exocytosis, binding of adhesion proteins and FV, FVIII, FIX, FX, but not anionic phospholipid exposure determined by flow cytometry. CD36 ligated specifically soluble fibrin, which recruited distinct coagulation factors via thiols. Selected patients with CKD showed elevated soluble fibrin plasma levels and enhanced thrombin-induced thrombin generation, which was normalized by CD36 blocking. Thus, CD36 is an important amplifier of platelet-dependent thrombin generation when exposure of anionic phospholipids is limited. This pathway might contribute to hypercoagulability in CKD.
凝血酶将纤维蛋白原转化为纤维蛋白，并在血栓炎症性疾病中激活血液和血管细胞。当被白细胞和血管细胞衍生的凝血酶激活时，血小板是凝血酶形成的放大器。血小板上的 CD36 充当带有损伤相关分子模式的分子的敏化剂，从而增加血小板反应性。在这里，我们研究了 CD36 在人血小板中凝血酶生成中的作用，包括患有晚期慢性肾脏病 (CKD) 的选定患者。缺乏 CD36 或被抗 CD36 抗体 FA6.152 阻断的血小板显示出在校准的自动血栓生成测定中由凝血酶触发的凝血酶生成受损。使用具有先天性功能缺陷的血小板、阻断抗体、药理学抑制剂和因子耗竭血浆，CD36 敏感的凝血酶生成依赖于 FXI、纤维蛋白以及通过 GPIbα 和 SFKs 的血小板信号转导。CD36 缺陷或阻断抑制了凝血酶诱导的血小板 αIIbβ3 激活、颗粒胞吐、粘附蛋白和 FV、FVIII、FIX、FX 的结合，但不通过流式细胞术确定阴离子磷脂的暴露。CD36 特异性地结合可溶性纤维蛋白，后者通过硫醇募集特定的凝血因子。选定的 CKD 患者显示出升高的可溶性纤维蛋白血浆水平和增强的凝血酶诱导的凝血酶生成，这通过 CD36 阻断得到正常化。因此，当阴离子磷脂暴露受到限制时，CD36 是血小板依赖性凝血酶生成的重要放大器。该途径可能导致 CKD 中的高凝状态。
