Characterization of hepatocyte growth factor activator inhibitors which are being developed for a medicine

据报道，肝细胞生长因子（HGF）的过度作用可引起肾损伤。因此，需要开发一种抑制HGF过度作用的药物。我们发现了两种新的蛋白酶抑制剂（HAI-1和HAI-2）可以抑制HGF激活剂的活性。在本研究中，我们考察了这些抑制剂是否可以作为HGF过度作用引起的疾病的药物，得到了以下结果：1。HAI-1具有两个Kunitz结构域，被认为是HAI-1蛋白酶抑制活性的功能结构域。为了确定Kunitz结构域在HAI-1对HGF激活剂抑制活性中的作用，我们构建了多种人HAI-1突变蛋白并检测了它们对HGF激活剂的抑制活性。n端Kunitz结构域具有较强的抑制活性，而c端Kunitz结构域具有较弱的抑制活性。HAI-2也有两个Kunitz域。我们还研究了Kunitz结构域在小鼠HAI-2对HGF激活剂的抑制活性中的作用。与人类HAI-1不同，c端Kunitz结构域具有较强的抑制活性，而n端Kunitz结构域的抑制活性较弱。因此，有必要研究HAI-1和HAI-2的哪个Kunitz结构域适用于某种药物。为了研究HAI的Kunitz结构域是否在体内抑制HGF的激活，需要建立实验动物的检测系统。我们观察大鼠注射HGF激活剂是否诱导HGF的激活。注射HGF激活剂诱导部分去肝大鼠肝脏中HGF的活化。该注射剂还能诱导肝脏再生。因此，该体系可用于测定HAI的Kunitz结构域的抑制活性。

It is reported that overaction of hepatocyte growth factor (HGF) causes kidney injury. Thus, it is required to develop a medicine which suppresses overaction of HGF. We identified two novel protease inhibitors (HAI-1 and HAI-2) which inhibit the activity of HGF activator. In this study, we examined whether these inhibitors could function as a medicine for diseases caused by overaction of HGF, and obtained the following results.1. HAI-1 has two Kunitz domains which are thought to be functional domains for the protease inhibitory activity of HAI-1. To determine the roles of the Kunitz domains in the inhibitory activity of HAI-1 against HGF activator, we constructed various human HAI-1 mutant proteins and examined their inhibitory activity against HGF activator. The N-terminal Kunitz domain had potent inhibitory activity, whereas the C-terminal Kunitz domain had only very weak activity. HAI-2 also has two Kunitz domains. We also examined the roles of Kunitz domains in the inhibitory activity of mouse HAI-2 against HGF activator. Unlike human HAI-1, the C-terminal Kunitz domain had potent inhibitory activity, whereas the N-terminal Kunitz domain had less activity. Therefore, it is necessary to examine which Kunitz domain of HAI-1 and HAI-2 is suitable for a medicine.2. To investigate whether the Kunitz domain of HAI suppresses activation of HGF in vivo, it is required to establish an assay system using experimental animals. We examined whether injection of HGF activator into rats induces activation of HGF. Injection of HGF activator induced activation of HGF in the liver of partially hepatectomized rats. This injection also induced liver regeneration. Therefore, this system would be useful to assay the inhibitory activity of the Kunitz domain of HAI.