Development of drug delivery systems for cytokines with an aim of efficient exertion of their pharmacological effect

在这一年里，我们试图阐明肝细胞生长因子(HGF)的消除机制，并根据其消除机制开发其药物释放系统。此外，我们还研究了粒细胞集落刺激因子(G-CSF)类似物的清除机制，G-CSF类似物目前被开发用于治疗癌症化疗中的骨抑制。为了研究肝细胞生长因子的清除机制，我们研究了其在大鼠肝部分切除后的药代动力学。根据体内和灌流肝脏系统的研究结果，我们证明受体介导的内吞作用和肝脏中的另一种非特异性摄取机制都有助于HGF的整体处置。此外，在肝脏疾病的情况下，如肝部分切除，通过前者机制的肝细胞生长因子清除显著下调，而通过后者机制的HGF清除维持…。高于正常水平(K.Liu等，Am.J.Physiol，269：G1-G9,1995)。后一种清除机制可能是细胞表面类肝素物质摄取HGF，不仅在肝实质细胞(肝细胞)中发现，而且在非实质细胞中也被发现。非实质细胞的非特异性摄取有助于HGF的处置，特别是在较高剂量下，这导致了HGF的药理作用(刘可欣等.药效12：1737-1740,1995)。为了抑制这种非特异性消除，HGF与肝素孵育形成肝素-HGF复合体，然后给ANIT处理的大鼠服用。肝素-HGF复合体给药后，肝脏损伤的几种标志酶水平(如GOT、GPT、ALP和LAP)较单用HGF后显著降低。肝素-HGF复合体注射后的血浆清除率明显低于单独注射HGF后的血浆清除量，提示这种肝素-HGF复合体可以作为HGF给药系统的候选药物(准备提交给杂志)。然而，通过标记指数技术评估对肝脏DNA合成的刺激作用在肝素-HGF复合体和单独的HGF之间是相似的，这意味着对于HGF的适当的药物传递系统需要进一步的研究。基于G-CSF类似物的药代动力学分析，我们发现G-CSF类似物的主要清除器官不是肝脏和肾脏，而是骨髓(T.Kuwabara等人.Am.J.Physiol.269：E1-E9,1995；T.Kuwabara等人.J.Pharmacol.Exher，273：1114-1122,1995)。较少

In this year, we atte mpted to clarify the elimination mechanism of hepatocyte growth factor (HGF), which is expected to be developed as a treatment for certain types of liver diseases, and to develop its drug delivery system considering its elimination mechanism. In addition, we also investigated the clearance mechanism for granulocyte-colony stimulating factor (G-CSF) analog, which is now developed as a treatment for bone suppression during cancer chemotherapy. To characterize the clearance mechanism of HGF,we examined its pharmacokinetics in rats after partial hepatectomy. Based on the findings in both in vivo and perfused liver system, we demonstrate that both receptor-mediated endocytosis and the other nonspecific uptake mechanism in the liver contribute to the over all disposition of HGF.Furthermore, in the liver-diseased conditions such as partial hepatectomy, HGF clearance via the former mechanism is dramatically downregulated while that via the latter mechanism is maintained a … More t the normal level (K.Liu et al.Am.j.Physiol., 269 : G1-G9,1995). The latter clearance mechanism, which is presumably the uptake of HGF by cell-surface heparin-like substance, is found out not only a the liver parenchymal cells (hepatocytes), but also at the non-parenchymal cells. The nonspecific uptake at the non-parenchymal cells contributs to the HGF disposition especially at the higher dose, which results in the pharmacological action of HGF (Ke-Xin Liu et al.Pharm.Res.12 : 1737-1740,1995). To suppress such a nonspecific elimination, HGF was incubated with heparin to form heparin-HGF complex, and subsequently administered into the ANIT-treated rats. Several marker enzyme levels for the livery injury (such as GOT,GPT,ALP,and LAP) were dramatically decreased after the administration of such heparin-HGF complex, compared with those values after the administration of HGF alone. Plasma clearance of HGF after the injection of complex was much lower than that after the injection of HGF alone, suggesting that this heparin-HGF complex can be a candidate for the drug delivery system for HGF (In preparation for submission to journal). However, stimulation of DNA synthesis in the liver, assessed by the labeling index technique, was comparable between for the heparin-HGF complex and HGF alone, implying that further studies are required for the adequate drug delivery system for HGF.Based on the pharmacokinetic analysis of the G-CSF analog, we found out that not the liver nor the kidney, but the bone marrow is the major clearance organ for G-CSF analog (T.Kuwabara et al.Am.J.Physiol., 269 : E1-E9,1995 ; T.Kuwabara et al.J.Pharmacol.Exp.Ther., 273 : 1114-1122,1995). Less