Hypercoagulability and vascular proinflammatory activation promote cardiac-cerebral fibrinogenesis in a rodent model of Chagas disease

Cardiomyopathy and stroke are major complications of Chagas disease (CD). We investigated if hypercoagulability, endothelial cell (EC) dysfunction, and blood stasis cause cardiac-cerebral fibrinogenesis in CD. C57BL/6 mice infected with Trypanosoma cruzi (Tc) were evaluated at acute (AT), indeterminate (IT), and chronic (CT) stages of CD. Mice were given anti-parasite, bicistronic immunogens (BCV or BCVR) to determine the role of Tc in fibrinogenesis. We monitored (1) platelet and coagulation cascade activation; (2) cardiac-cerebral blood vessels injury; (3) proinflammatory/prothrombotic phenotypes of microglia, macrophages, and vascular cells; and (4) fibrinogenesis. After a quiescent acute phase, plasma levels of coagulation and other factors of platelet activation/aggregation, hypercoagulability, and clotting capacity were increased in IT–CT mice. Proinflammatory and prothrombotic cytokines/chemokines in cardiac-cerebral blood vessels were also significantly increased in IT–CT mice. Loss of cardiac EC and a marked increase in their proinflammatory/cell-adhesion response were not compensated for by a pro-angiogenic/wound-healing response in cardiac-cerebral tissues of infected mice. Microglial proinflammatory activation preceded the vascular inflammation suggesting a feedback cycle of EC activation in brain of infected mice. Treatment with BCV/BCVR controlled the parasite persistence and hypercoagulability/vascular inflammation in infected mice. Importantly, BCV/BCVR treatment abolished the fibrin clots that otherwise were pronounced in heart and brain of IT–CD mice. We conclude that acute Tc infection triggered a subdued hemodynamic disorder, and the persistence of low-grade parasites contributed to a cardiovascular/cerebrovascular proinflammatory and prothrombotic response and fibrin deposition in mice. BCV/BCVR offer potential immunotherapies for reducing the recurrent clot formation and risk of stroke in CD.心肌病与脑卒中是恰加斯病（Chagas disease, CD）的主要并发症。本研究旨在探讨高凝状态（hypercoagulability）、内皮细胞（endothelial cell, EC）功能障碍及血液淤滞是否介导了CD患者的心脑血管纤维蛋白生成过程。我们对感染克氏锥虫（Trypanosoma cruzi, Tc）的C57BL/6小鼠，分别在CD的急性期（acute phase, AT）、隐匿期（indeterminate phase, IT）与慢性期（chronic phase, CT）进行检测评估。为明确Tc在纤维蛋白生成过程中的作用，我们为小鼠施用了抗寄生虫双顺反子免疫原（bicistronic immunogens，BCV或BCVR）。我们对以下四项指标进行了监测：(1) 血小板（platelet）与凝血级联激活状态；(2) 心脑血管损伤程度；(3) 小胶质细胞（microglia）、巨噬细胞（macrophages）及血管细胞的促炎/促血栓表型（proinflammatory/prothrombotic phenotypes）；(4) 纤维蛋白生成水平。在静止性急性期过后，隐匿期-慢性期（IT–CT）小鼠的血浆凝血因子、血小板激活/聚集相关因子水平、高凝状态指标及凝血能力均显著升高。心脑血管组织中的促炎与促血栓细胞因子/趋化因子（cytokines/chemokines）水平，同样在IT–CT小鼠中显著上调。感染小鼠的心脑血管组织中，心脏EC的缺失及其促炎/细胞黏附反应的显著增强，并未被促血管生成/创伤愈合反应所代偿。在感染小鼠的脑组织中，小胶质细胞的促炎激活先于血管炎症发生，提示存在EC激活的反馈循环。施用BCV/BCVR可有效控制感染小鼠的寄生虫持续感染与高凝状态、血管炎症反应。尤为重要的是，BCV/BCVR治疗可消除本应在隐匿期CD（IT–CD）小鼠心脑组织中大量形成的纤维蛋白凝块。本研究得出结论：急性Tc感染可引发轻度血流动力学紊乱，而低水平寄生虫的持续感染会导致小鼠出现心血管/脑血管的促炎及促血栓反应，并伴随纤维蛋白沉积。BCV/BCVR有望成为潜在的免疫治疗手段，用于降低CD患者的复发性血栓形成风险与脑卒中发生风险。