Neurotoxic effects of exogenous tissue-type plasminogen activator on the normal brain

组织型纤溶酶原激活剂(TPA)静脉和动脉内给药溶栓治疗急性缺血性卒中已被建立。TPA也被认为具有神经毒性作用。本研究的目的是通过微透析探头将tPA灌流到大脑皮层后，检测tPA引起的神经毒性。成年雄性Wistar大鼠分为3组：(A)大剂量(30μ/L)tPA组，(B)低剂量(15μ/L)tPA组，(C)对照组(生理盐水)。苏木精-伊红(HE)染色切片图像分析对病变体积进行组织学定量。静脉注射伊文思蓝评价TPA对血脑屏障(BBB)的破坏作用。用抗层粘连蛋白抗体的免疫组织化学方法评价基底板的损伤程度。同时还观察了tPA灌流后一氧化氮(NO)合成的动态变化。对照组中，除探针束外，未见其他结构改变。在两个tPA组，探针周围都有苍白的病变，显微镜下可见神经元出现坏死性改变。大剂量tPA组病变体积明显增大。在rtPA灌流的动物中观察到明显的伊文思蓝外渗。在tPA诱导的损伤中，血管层粘连蛋白免疫反应消失。TPA灌流后NO终末产物水平明显升高。这些结果提供了tPA的直接神经毒性的证据，也表明tPA引起血脑屏障的破坏和基底膜的损伤，从而增加了水肿的形成。

Thrombolytic therapy with intravenous and intra-arterial administration of tissue-type plasminogen activator (tPA) has been established for the treatment of acute ischemic stroke. tPA has also been suggested to have neurotoxic effects. The purpose of this study was to examine tPA-induced neurotoxicity after perfusion into the cortex via a microdialysis probe. Adult male Wistar rats were divided into three groups : (a)high-dose (30 μmol/l) tPA group ; (b)low-dose (15μ mol/l) tPA ; (c)control (physiological saline) group. The volume of the lesion was quantified histologically by image analysis of hematoxylin and eosin (HE)-stained sections. tPA-induced blood-brain barrier (BBB) disruption was evaluated by intravenous injection of Evans blue. Injury of the basal lamina was evaluated by immunohistochemistry using an anti-laminin antibody. Sequential changes in nitric oxide (NO) synthesis following tPA perfusion was also investigated. In the control group, no structural change was observed except for the probe tract. In both tPA groups, a pale lesion was produced around the probe, and microscopically, neurons showed necrotic changes. The volume of the lesions was significantly higher in the high-dose tPA group. Marked and extensive extravasation of Evans blue was observed in the rtPA-perfused animals. Laminin immunoreactivity of blood vessels in the tPA-induced lesions was lost. The level of NO end-products was increased markedly after tPA perfusion. These results provide evidence of direct neurotoxicity of tPA, and also suggest that tPA causes BBB disruption and injury of the basal lamina, thereby increasing edema formation.