Seyfried D, Han Y, Zheng Z, Day N, Moin K, Rempel S, Sloane B, Chopp M
Department of Neurosurgery, Henry Ford Health Sciences Center, Wayne State University, Detroit, Michigan 48202, USA.
J Neurosurg. 1997 Nov;87(5):716-23. doi: 10.3171/jns.1997.87.5.0716.
Lysosomal proteases, although tightly regulated under physiological conditions, are known to contribute to cell injury after various forms of tissue ischemia have occurred. Because cathepsin B is a prominent lysosomal protease found in brain parenchyma, the authors hypothesized that it may contribute to neuronal cell death after focal cerebral ischemia. The authors measured the expression and spatial distribution of cathepsin B within the ischemic brain in 43 animals by means of immunohistochemical analysis in a rat model of transient middle cerebral artery (MCA) occlusion. Cathepsin B activity was also measured within specific ischemic brain regions by using an in vitro assay (22 animals). In addition, the authors tested the therapeutic effect of preischemic intraventricular administration of stefin A, a cysteine protease inhibitor, on the volume of cerebral infarction after transient MCA occlusion (15 animals). Increased cathepsin B immunoreactivity was detected exclusively within the ischemic neurons after 2 hours of reperfusion following a 2-hour MCA occlusion. Cathepsin B immunolocalization in the ischemic region decreased by 24 hours of reperfusion, but then increased by 48 hours of reperfusion because the infarct was infiltrated by inflammatory cells. Increased immunolocalization of cathepsin B in the inflammatory cells located in the necrotic infarct core continued through 7 days of reperfusion. Cathepsin B enzymatic activity was significantly increased in the ischemic tissue at 2, 8, and 48 hours, but not at 24 hours of reperfusion after 2 hours of MCA occlusion. Continuous intraventricular infusion of stefin A, before 2 hours of MCA occlusion (15 animals), significantly reduced infarct volume compared with control animals (12 animals): the percentage of hemispheric infarct volume was 20+/-3.9 compared with 33+/-3.5 (standard error of the mean; p = 0.025). These data indicate that neuronal cathepsin B undergoes increased expression and activation within 2 hours of reperfusion after a 2-hour MCA occlusion and may be a mechanism contributing to neuronal cell death. Intraventricular infusion of stefin A, an inhibitor of cathepsin B, significantly reduces cerebral infarct volume in rats.
溶酶体蛋白酶虽然在生理条件下受到严格调控，但已知在各种形式的组织缺血发生后会导致细胞损伤。由于组织蛋白酶B是在脑实质中发现的一种突出的溶酶体蛋白酶，作者推测它可能在局灶性脑缺血后导致神经元细胞死亡。作者通过免疫组织化学分析，在短暂性大脑中动脉（MCA）闭塞的大鼠模型中，测量了43只动物缺血脑内组织蛋白酶B的表达和空间分布。还通过体外试验测量了特定缺血脑区的组织蛋白酶B活性（22只动物）。此外，作者测试了缺血前脑室内注射半胱氨酸蛋白酶抑制剂斯他汀A对短暂性MCA闭塞后脑梗死体积的治疗效果（15只动物）。在MCA闭塞2小时后再灌注2小时，仅在缺血神经元内检测到组织蛋白酶B免疫反应性增加。缺血区的组织蛋白酶B免疫定位在再灌注24小时时降低，但在再灌注48小时时增加，因为梗死区被炎性细胞浸润。位于坏死梗死核心的炎性细胞中组织蛋白酶B的免疫定位增加持续到再灌注7天。在MCA闭塞2小时后，缺血组织中组织蛋白酶B的酶活性在再灌注2、8和48小时时显著增加，但在24小时时未增加。在MCA闭塞2小时前持续脑室内输注斯他汀A（15只动物），与对照动物（12只动物）相比，梗死体积显著减小：半球梗死体积百分比为20±3.9，而对照动物为33±3.5（均值标准误；p = 0.025）。这些数据表明，在MCA闭塞2小时后再灌注的2小时内，神经元组织蛋白酶B的表达和激活增加，可能是导致神经元细胞死亡的一种机制。脑室内输注组织蛋白酶B抑制剂斯他汀A可显著减小大鼠的脑梗死体积。
