Ohnishi Masatoshi, Katsuki Hiroshi, Fujimoto Shinji, Takagi Mikako, Kume Toshiaki, Akaike Akinori
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan.
Exp Neurol. 2007 Jul;206(1):43-52. doi: 10.1016/j.expneurol.2007.03.030. Epub 2007 Apr 14.
Thrombin is thought to play an important role in brain damage associated with intracerebral hemorrhage (ICH). We previously showed that activation of mitogen-activated protein (MAP) kinases and recruitment of microglia are crucial for thrombin-induced shrinkage of the striatal tissue in vitro and thrombin-induced striatal damage in vivo. Here we investigated whether the same mechanisms are involved in ICH-induced brain injury. A substantial loss of neurons was observed in the center and the peripheral region of hematoma at 3 days after ICH induced by intrastriatal injection of collagenase in adult rats. Intracerebroventricular injection of argatroban or cycloheximide, both of which prevent thrombin cytotoxicity in vitro, exhibited a significant neuroprotective effect against ICH-induced injury. ICH-induced neuron loss was also prevented by a MAP kinase kinase inhibitor (PD98059) and a c-Jun N-terminal kinase inhibitor (SP600125). These drugs had no effect on hematoma size or ICH-induced brain edema. Activation of extracellular signal-regulated kinase in response to ICH was observed in both neurons and microglia. Despite their neuroprotective effects, MAP kinase inhibitors did not decrease the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells appearing after ICH. Identification of cell types revealed that TUNEL staining occurred prominently in neurons but not in microglia, whereas inhibition of MAP kinases resulted in appearance of TUNEL staining in microglia. These results suggest that thrombin and the activation of MAP kinases are involved in ICH-induced neuronal injury, and that neuroprotective effects of MAP kinases are in part mediated by arrestment of microglial activities.
凝血酶被认为在与脑出血（ICH）相关的脑损伤中起重要作用。我们先前表明，丝裂原活化蛋白（MAP）激酶的激活和小胶质细胞的募集对于凝血酶在体外诱导的纹状体组织收缩以及在体内诱导的纹状体损伤至关重要。在此，我们研究了相同的机制是否参与ICH诱导的脑损伤。成年大鼠纹状体内注射胶原酶诱导ICH后3天，在血肿中心和周边区域观察到大量神经元丢失。脑室内注射阿加曲班或环己酰亚胺，这两种药物均可在体外预防凝血酶的细胞毒性，对ICH诱导的损伤均表现出显著的神经保护作用。MAP激酶激酶抑制剂（PD98059）和c-Jun N末端激酶抑制剂（SP600125）也可预防ICH诱导的神经元丢失。这些药物对血肿大小或ICH诱导的脑水肿无影响。在神经元和小胶质细胞中均观察到ICH诱导的细胞外信号调节激酶激活。尽管MAP激酶抑制剂具有神经保护作用，但它们并未减少ICH后出现的末端脱氧核苷酸转移酶介导的dUTP缺口末端标记（TUNEL）阳性细胞数量。细胞类型鉴定显示，TUNEL染色主要发生在神经元而非小胶质细胞中，而抑制MAP激酶则导致小胶质细胞中出现TUNEL染色。这些结果表明，凝血酶和MAP激酶的激活参与了ICH诱导的神经元损伤，并且MAP激酶的神经保护作用部分是由小胶质细胞活性的抑制介导的。
