Cell biological control of chronic glomerulonephritis -Analysis of signal transduction molecules in pletelets and glomerular cells-

血管紧张素II （Angiotensin II， AII）引起囊膜细胞的收缩和增殖，这两者在慢性肾小球肾炎的病因学和病理生理学中都很重要。近年来的研究表明，磷酸肌肽周期（PI周期）的激活是包括AII在内的钙动员激素的共同信号转导机制。这种可能性已被认为是调节PI代谢导致慢性肾小球肾炎的新疗法的发现。不幸的是，之前发表的测量肌醇磷酸（IPs）的方法有一些缺点，这些方法应该为活化的PI循环提供直接证据，即磷脂酶c催化磷脂酰肌醇4,5-二磷酸的水解。因此，在本研究项目中，我们开发了一种新的高效液相色谱（HPLC）方法，通过该方法我们可以评估aii诱导培养的大鼠系膜细胞IPS的变化。新建立的高效液相色谱法可以分析肌醇1,4,5-三磷酸（Ins(1,4,5)P_3）、肌醇1,3,4-三磷酸（Ins(1,3,4)P_3）、肌醇1,3,4,5-四磷酸（Ins(1,3,4,5)P_4）、肌醇五磷酸（IP_5）和肌醇六磷酸（IP_6）的变化。当10-7 M AII作用于细胞时，Ins(1,4,5)P_3的增加是非常迅速和短暂的。Ins(1、3、4、5)P_4的增加也很快，持续时间长达60秒，Ins(1、3、4)P_4的增加也紧随其后。单磷酸肌醇和二磷酸肌醇也分别在30秒和5秒内增加。IP_5和IP_6均未因AII而升高。AII诱导的IP_1、IP_2和肌醇三磷酸的增加呈剂量依赖性，并被AII竞争抑制剂萨拉霉素完全抑制。综上所述，我们认为在培养的大鼠系膜细胞中，包括肌醇三磷酸途径和四磷酸途径在内的PI周期是AII的信号转导机制，它可能与细胞的收缩和增殖相结合。少

Angiotensin II ( AII ) causes the contraction and proliferation of msangial cells, both of which are important in etiology and pathophysiology of chronic glomerulonephritis. Recently lines of evidenc have revealed thath the activation of phosphoinositide cycle ( PI cycle ) is a common signal transduction mechanism in the action of Ca-mobilizing hormones including AII. The possibility has been suggested that the modulation of PI metabolism leads to the discovery of new therapy for chronic glomerulonephritis. Unfortunately, the proeviously published methods for the measurement of inositol phosphates ( IPs ), which should provide direct evidence for activated PI cycle, i.e., phospholipase C-catalyzed hydrolysis of phosphatidylinositol 4,5-bisphosphate, had some disadvantages.In this research project, therefore, we developed the new high performance liquid chromatography ( HPLC ) method, by which we could evaluate AII-induced changes in IPS in cultured rat mesangial cells. The newly develo … More ped HPLC method has enable us to analyze the change in IPs including inositol 1,4,5-trisphosphate ( Ins(1,4,5)P_3 ), inositol 1,3,4-trisphosphate ( Ins(1,3,4)P_3 ), inositol 1,3,4,5-tetrakisphosphate ( Ins(1,3,4,5)P_4 ), inositol pentakisphosphate ( IP_5 ) and inositol hexakisphosphate ( IP_6 ).When the cells were treated with 10-7 M AII, the increase of Ins(1,4,5)P_3 was very rapid and transient. The increase of Ins(1,3,4,5)P_4 was also rapid and remained increased for up to 60 sec. The increase of Ins(1,3,4)P_4 followed their increases. Inositol monophosphate and inositol bisphosphate also increased within 30 sec and 5 sec, respectively. Neither IP_5 nor IP_6 was increased by AII. AII-induced increase of IP_1, IP_2 and inositol trisphosphate showed dose-dependency and were completely inhibited by saralasin, the competitive inhibitor for AII.From these results, we suggest that in cultured rat mesangial cells PI cycle including inositol tris- and tetrakisphosphate pathway is the signal transduction mechanism for AII, which may be coupled with the contraction and proliferation ff the cells. Less