Hopp Sarah, Nolte Marc W, Stetter Christian, Kleinschnitz Christoph, Sirén Anna-Leena, Albert-Weissenberger Christiane
Department of Neurology, University Hospital Würzburg, Würzburg, Germany.
Department of Neurosurgery, University Hospital Würzburg, Josef-Schneider-Strasse 11, Würzburg, Germany.
J Neuroinflammation. 2017 Feb 20;14(1):39. doi: 10.1186/s12974-017-0815-8.
Traumatic brain injury (TBI) is a devastating neurological condition and a frequent cause of permanent disability. Posttraumatic inflammation and brain edema formation, two pathological key events contributing to secondary brain injury, are mediated by the contact-kinin system. Activation of this pathway in the plasma is triggered by activated factor XII. Hence, we set out to study in detail the influence of activated factor XII on the abovementioned pathophysiological features of TBI.
Using a cortical cryogenic lesion model in mice, we investigated the impact of genetic deficiency of factor XII and inhibition of activated factor XII with a single bolus injection of recombinant human albumin-fused Infestin-4 on the release of bradykinin, the brain lesion size, and contact-kinin system-dependent pathological events. We determined protein levels of bradykinin, intracellular adhesion molecule-1, CC-chemokine ligand 2, and interleukin-1β by enzyme-linked immunosorbent assays and mRNA levels of genes related to inflammation by quantitative real-time PCR. Brain lesion size was determined by tetrazolium chloride staining. Furthermore, protein levels of the tight junction protein occludin, integrity of the blood-brain barrier, and brain water content were assessed by Western blot analysis, extravasated Evans Blue dye, and the wet weight-dry weight method, respectively. Infiltration of neutrophils and microglia/activated macrophages into the injured brain lesions was quantified by immunohistological stainings.
We show that both genetic deficiency of factor XII and inhibition of activated factor XII in mice diminish brain injury-induced bradykinin release by the contact-kinin system and minimize brain lesion size, blood-brain barrier leakage, brain edema formation, and inflammation in our brain injury model.
Stimulation of bradykinin release by activated factor XII probably plays a prominent role in expanding secondary brain damage by promoting brain edema formation and inflammation. Pharmacological blocking of activated factor XII could be a useful therapeutic principle in the treatment of TBI-associated pathologic processes by alleviating posttraumatic inflammation and brain edema formation.
创伤性脑损伤（TBI）是一种毁灭性的神经系统疾病，也是导致永久性残疾的常见原因。创伤后炎症和脑水肿形成是导致继发性脑损伤的两个病理关键事件，由接触激肽系统介导。血浆中该途径的激活由活化因子XII触发。因此，我们着手详细研究活化因子XII对TBI上述病理生理特征的影响。
使用小鼠皮质冷冻损伤模型，我们研究了因子XII基因缺陷以及单次推注重组人白蛋白融合的Infestin-4对活化因子XII的抑制作用，对缓激肽释放、脑损伤大小以及接触激肽系统依赖性病理事件的影响。我们通过酶联免疫吸附测定法测定缓激肽、细胞间黏附分子-1、CC趋化因子配体2和白细胞介素-1β的蛋白质水平，并通过定量实时PCR测定与炎症相关基因的mRNA水平。通过氯化四氮唑染色确定脑损伤大小。此外，分别通过蛋白质印迹分析、渗出的伊文思蓝染料和湿重-干重法评估紧密连接蛋白闭合蛋白的蛋白质水平、血脑屏障的完整性和脑含水量。通过免疫组织化学染色对中性粒细胞和小胶质细胞/活化巨噬细胞浸润到受伤脑损伤中的情况进行定量。
我们表明，在我们的脑损伤模型中，小鼠体内因子XII的基因缺陷和活化因子XII的抑制均可减少脑损伤诱导的接触激肽系统缓激肽释放，并使脑损伤大小、血脑屏障渗漏、脑水肿形成和炎症最小化。
活化因子XII刺激缓激肽释放可能通过促进脑水肿形成和炎症在扩大继发性脑损伤中起重要作用。对活化因子XII进行药理阻断可能是治疗TBI相关病理过程的有用治疗原则，可减轻创伤后炎症和脑水肿形成。
