Masamune Atsushi, Kikuta Kazuhiro, Satoh Masahiro, Kume Kiyoshi, Shimosegawa Tooru
Pancreas Research Group, Division of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
Tohoku J Exp Med. 2003 Feb;199(2):69-84. doi: 10.1620/tjem.199.69.
Activated pancreatic stellate cells (PSCs) have recently been implicated in the pathogenesis of pancreatic fibrosis and inflammation. Accumulation of PSCs is a fundamental feature of pancreatic fibrosis, and platelet-derived growth factor (PDGF)-BB is the most potent mitogen for PSCs. But, the molecular mechanisms responsible for PDGF's actions in PSCs are largely unknown. In hepatic stellate cells, it has been established that activation of both phosphatidylinositol (PI) 3-kinase and extracellular-signal regulated kinase (ERK) pathways is required for PDGF-BB-induced proliferation and migration. The aim of this study was to elucidate the signaling pathways mediating PDGF-BB's actions in PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype. Culture-activated PSCs expressed PDGF alpha- and beta-receptors. PDGF-BB induced autophosphorylation of its receptor, followed by the activation of PI 3-kinase, Akt, and ERK pathways. Activation of PI 3-kinase was not required for PDGF-BB-induced ERK activation. PDGF-BB induced approximately five-fold increase in proliferation and chemotaxis of PSCs. Inhibition of ERK pathway with PD98059 completely blocked proliferation, whereas PD98059 had a modest inhibitory effect on cell migration (approximately 50%). On the other hand, inhibition of PI 3-kinase pathway with wortmannin or LY294002 almost completely inhibited migration, but did not affect proliferation of PSCs. In conclusion, our results suggest that ERK pathway regulates proliferation and migration in response to PDGF-BB, whereas PI 3-kinase mediates cellular migration, but not proliferation of PSCs.
活化的胰腺星状细胞（PSCs）最近被认为与胰腺纤维化和炎症的发病机制有关。PSCs的积累是胰腺纤维化的一个基本特征，血小板衍生生长因子（PDGF）-BB是对PSCs最有效的促有丝分裂原。但是，PDGF在PSCs中发挥作用的分子机制在很大程度上尚不清楚。在肝星状细胞中，已经证实磷脂酰肌醇（PI）3激酶和细胞外信号调节激酶（ERK）途径的激活是PDGF-BB诱导增殖和迁移所必需的。本研究的目的是阐明介导PDGF-BB在PSCs中作用的信号通路。从大鼠胰腺组织中分离出PSCs，并以其培养活化的肌成纤维细胞样表型使用。培养活化的PSCs表达PDGFα和β受体。PDGF-BB诱导其受体的自磷酸化，随后激活PI 3激酶、Akt和ERK途径。PDGF-BB诱导的ERK激活不需要PI 3激酶的激活。PDGF-BB诱导PSCs的增殖和趋化性增加约五倍。用PD98059抑制ERK途径完全阻断了增殖，而PD98059对细胞迁移有适度的抑制作用（约50%）。另一方面，用渥曼青霉素或LY294002抑制PI 3激酶途径几乎完全抑制了迁移，但不影响PSCs的增殖。总之，我们的结果表明，ERK途径调节对PDGF-BB的增殖和迁移反应，而PI 3激酶介导细胞迁移，但不介导PSCs的增殖。
