Niego Be'eri, Broughton Brad R S, Ho Heidi, Sobey Christopher G, Medcalf Robert L
Molecular Neurotrauma and Haemostasis, Australian Centre for Blood Diseases, Monash University, Level 4 Burnet Building, 89 Commercial Road, Melbourne, 3004, VIC, Australia.
Cardiovascular & Pulmonary Pharmacology Group, Biomedicine Discovery Institute, Department of Pharmacology, Monash University, Clayton, VIC, Australia.
Fluids Barriers CNS. 2017 Nov 21;14(1):33. doi: 10.1186/s12987-017-0081-2.
Symptomatic intracerebral haemorrhage (sICH) following tissue-type plasminogen activator (rt-PA) administration is the most feared and lethal complication of thrombolytic therapy for ischaemic stroke, creating a significant obstacle for a broader uptake of this beneficial treatment. rt-PA also undermines cerebral vasculature stability in a multimodal process which involves engagement with LDL receptor-related protein 1 (LRP-1), potentially underlying the development of sICH.
We aimed to simulate rt-PA-induced haemorrhagic transformation (HT) in a mouse model of stroke and to assess if it drives symptomatic neurological deterioration and whether it is attenuated by LDL receptor blockade. rt-PA (10 mg/kg) or its vehicle, with or without the LDL receptor antagonist, receptor-associated protein (RAP; 2 mg/kg), were intravenously injected at reperfusion after 0.5 or 4 h of middle cerebral artery occlusion (MCAo). Albumin and haemoglobin content were measured in the perfused mouse brains 24 h post MCAo as indications of blood-brain barrier (BBB) compromise and HT, respectively.
rt-PA did not elevate brain albumin and haemoglobin levels in sham mice or in mice subjected to 0.5 h MCAo. In contrast, administration of rt-PA after prolonged MCAo (4 h) caused a marked increase in HT (but similar changes in brain albumin) compared to vehicle, mimicking the clinical shift from a safe to detrimental intervention. Interestingly, this HT did not correlate with functional deficit severity at 24 h, suggesting that it does not play a symptomatic role in our mouse stroke model. Co-administration of RAP with or without rt-PA reduced mortality and neurological scores but did not effectively decrease brain albumin and haemoglobin levels.
Despite the proven causative relationship between severe HT and neurological deterioration in human stroke, rt-PA-triggered HT in mouse MCAo does not contribute to neurological deficit or simulate sICH. Model limitations, such as the long duration of occlusion required, the type of HT achieved and the timing of deficit assessment may account for this mismatch. Our results further suggest that blockade of LDL receptors improves stroke outcome irrespective of rt-PA, blood-brain barrier breakdown and HT.
组织型纤溶酶原激活剂（rt-PA）给药后发生的症状性脑出血（sICH）是缺血性中风溶栓治疗最可怕且致命的并发症，严重阻碍了这种有益治疗方法的广泛应用。rt-PA还会通过涉及与低密度脂蛋白受体相关蛋白1（LRP-1）相互作用的多模式过程破坏脑血管稳定性，这可能是sICH发生的潜在原因。
我们旨在模拟中风小鼠模型中rt-PA诱导的出血性转化（HT），并评估其是否会导致症状性神经功能恶化，以及低密度脂蛋白受体阻断是否能减轻这种情况。在大脑中动脉闭塞（MCAo）0.5或4小时后再灌注时，静脉注射rt-PA（10mg/kg）或其溶媒，同时给予或不给予低密度脂蛋白受体拮抗剂受体相关蛋白（RAP；2mg/kg）。在MCAo后24小时测量灌注小鼠大脑中的白蛋白和血红蛋白含量，分别作为血脑屏障（BBB）受损和HT的指标。
rt-PA在假手术小鼠或MCAo 0.5小时的小鼠中未升高脑白蛋白和血红蛋白水平。相比之下，与溶媒相比，长时间MCAo（4小时）后给予rt-PA导致HT显著增加（但脑白蛋白变化相似），模拟了从安全干预到有害干预的临床转变。有趣的是，这种HT与24小时时的功能缺损严重程度无关，表明它在我们的小鼠中风模型中不发挥症状性作用。RAP与rt-PA联合或不联合给药可降低死亡率和神经评分，但并未有效降低脑白蛋白和血红蛋白水平。
尽管在人类中风中已证实严重HT与神经功能恶化之间存在因果关系，但在小鼠MCAo模型中rt-PA引发的HT并不导致神经功能缺损或模拟sICH。模型的局限性，如所需的闭塞时间长、实现的HT类型以及缺损评估的时间，可能是造成这种差异的原因。我们的结果进一步表明，无论rt-PA、血脑屏障破坏和HT如何，阻断低密度脂蛋白受体均可改善中风结局。
