Zhu Shu, Travers Richard J, Morrissey James H, Diamond Scott L
Department of Chemical and Biomolecular Engineering, and Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA; and.
Department of Biochemistry, University of Illinois, Urbana, IL.
Blood. 2015 Sep 17;126(12):1494-502. doi: 10.1182/blood-2015-04-641472. Epub 2015 Jul 1.
Factor XIIa (FXIIa) and factor XIa (FXIa) contribute to thrombosis in animal models, whereas platelet-derived polyphosphate (polyP) may potentiate contact or thrombin-feedback pathways. The significance of these mediators in human blood under thrombotic flow conditions on tissue factor (TF) -bearing surfaces remains inadequately resolved. Human blood (corn trypsin inhibitor treated [4 μg/mL]) was tested by microfluidic assay for clotting on collagen/TF at TF surface concentration ([TF]wall) from ∼0.1 to 2 molecules per μm(2). Anti-FXI antibodies (14E11 and O1A6) or polyP-binding protein (PPXbd) were used to block FXIIa-dependent FXI activation, FXIa-dependent factor IX (FIX) activation, or platelet-derived polyP, respectively. Fibrin formation was sensitive to 14E11 at 0 to 0.1 molecules per µm(2) and sensitive to O1A6 at 0 to 0.2 molecules per µm(2). However, neither antibody reduced fibrin generation at ∼2 molecules per µm(2) when the extrinsic pathway became dominant. Interestingly, PPXbd reduced fibrin generation at low [TF]wall (0.1 molecules per µm(2)) but not at zero or high [TF]wall, suggesting a role for polyP distinct from FXIIa activation and requiring low extrinsic pathway participation. Regardless of [TF]wall, PPXbd enhanced fibrin sensitivity to tissue plasminogen activator and promoted clot retraction during fibrinolysis concomitant with an observed PPXbd-mediated reduction of fibrin fiber diameter. This is the first detection of endogenous polyP function in human blood under thrombotic flow conditions. When triggered by low [TF]wall, thrombosis may be druggable by contact pathway inhibition, although thrombolytic susceptibility may benefit from polyP antagonism regardless of [TF]wall.
在动物模型中，因子Ⅻa（FXIIa）和因子Ⅺa（FXIa）会导致血栓形成，而血小板衍生的多聚磷酸盐（polyP）可能会增强接触或凝血酶反馈途径。在血栓形成血流条件下，这些介质在人血液中对含组织因子（TF）表面的作用仍未得到充分阐明。通过微流控分析检测了人血液（经玉米胰蛋白酶抑制剂处理[4μg/mL]）在胶原蛋白/TF上的凝血情况，TF表面浓度（[TF]壁）约为每μm²0.1至2个分子。分别使用抗FXI抗体（14E11和O1A6）或多聚磷酸盐结合蛋白（PPXbd）来阻断FXIIa依赖性FXI激活、FXIa依赖性因子Ⅸ（FIX）激活或血小板衍生的多聚磷酸盐。纤维蛋白形成在每μm²0至0.1个分子时对14E11敏感，在每μm²0至0.2个分子时对O1A6敏感。然而，当外源性途径占主导时，在每μm²约2个分子时，这两种抗体均未减少纤维蛋白生成。有趣的是，PPXbd在低[TF]壁（每μm²0.1个分子）时减少了纤维蛋白生成，但在零或高[TF]壁时未减少，这表明多聚磷酸盐具有不同于FXIIa激活的作用，且需要低外源性途径参与。无论[TF]壁如何，PPXbd均增强了纤维蛋白对组织型纤溶酶原激活剂的敏感性，并在纤维蛋白溶解过程中促进了凝块回缩，同时观察到PPXbd介导的纤维蛋白纤维直径减小。这是首次在血栓形成血流条件下检测到人血液中内源性多聚磷酸盐的功能。当由低[TF]壁触发时，尽管无论[TF]壁如何，溶栓敏感性可能受益于多聚磷酸盐拮抗作用，但通过接触途径抑制可能可使血栓形成成为可药物治疗的靶点。
