Gentilini A, Feliers D, Pinzani M, Woodruff K, Abboud S
Department of Medicine, University of Texas Health Science Center, San Antonio, 78284, USA.
J Cell Physiol. 1998 Feb;174(2):240-50. doi: 10.1002/(SICI)1097-4652(199802)174:2<240::AID-JCP11>3.0.CO;2-G.
Cultured hepatic stellate cells (HSCs), the cell type primarily involved in the progression of liver fibrosis, secrete insulin-like growth factor-I (IGF-I) and IGF binding protein (IGFBP) activity. IGF-I exerts a mitogenic effect on HSCs, thus potentially contributing to the fibrogenic process in an autocrine fashion. However, IGF-I action is modulated by the presence of specific IGFBPs that may inhibit and/or enhance its biologic effects. Therefore, we examined IGFBP-1 through IGFBP-6 mRNA and protein expression in HSCs isolated from human liver and activated in culture. Regulation of IGFBPs in response to IGF-I and other polypeptide growth factors involved in the hepatic fibrogenic process was also assessed. RNase protection assays and ligand blot analysis demonstrated that HSCs express IGFBP-2 through IGFBP-6 mRNAs and release detectable levels of IGFBP-2 through IGFBP-5. Because IGF-I, platelet-derived growth factor-BB (PDGF-BB), and transforming growth factor-beta (TGF-beta) stimulate HSC proliferation and/or matrix production, we tested their effect on IGFBPs released by HSCs. IGF-I induced IGFBP-3 and IGFBP-5 proteins in a time-dependent manner without an increase in the corresponding mRNAs. IGFBP-4 protein levels decreased in response to IGF-I. TGF-beta stimulated IGFBP-3 mRNA and protein but decreased IGFBP-5 mRNA and protein. In contrast, PDGF-BB failed to regulate IGFBPs compared with controls. Recombinant human IGFBP-3 (rhIGFBP-3) was then tested for its effect on IGF-I-induced mitogenesis in HSCs. rhIGFBP-3 inhibited IGF-I-stimulated DNA synthesis in a dose-dependent manner, with a peak effect observed at 25 nM IGFBP-3. Because TGF-beta is highly expressed in cirrhotic liver tissue, we determined whether IGFBP-3 mRNA expression is increased in liver biopsies obtained from patients with an active fibroproliferative response due to viral-induced chronic active hepatitis. In the majority of these samples, IGFBP-3 mRNA was increased compared with normal controls. These findings indicate that human HSCs, in their activated phenotype, constitutively produce IGFBPs. IGF-I and TGF-beta differentially regulate IGFBP-3, IGFBP-4, and IGFBP-5 expression, which, in turn, may modulate the in vitro and in vivo action of IGF-I.
培养的肝星状细胞（HSCs）是主要参与肝纤维化进展的细胞类型，可分泌胰岛素样生长因子-I（IGF-I）和IGF结合蛋白（IGFBP）活性。IGF-I对HSCs具有促有丝分裂作用，因此可能以自分泌方式促进纤维化进程。然而，IGF-I的作用受到特定IGFBPs的调节，这些IGFBPs可能抑制和/或增强其生物学效应。因此，我们检测了从人肝脏分离并在培养中激活的HSCs中IGFBP-1至IGFBP-6的mRNA和蛋白表达。还评估了IGFBPs对IGF-I和其他参与肝纤维化进程的多肽生长因子的反应调节。核糖核酸酶保护试验和配体印迹分析表明，HSCs表达IGFBP-2至IGFBP-6的mRNA，并释放可检测水平的IGFBP-2至IGFBP-5。由于IGF-I、血小板衍生生长因子-BB（PDGF-BB）和转化生长因子-β（TGF-β）刺激HSC增殖和/或基质产生，我们测试了它们对HSCs释放的IGFBPs的影响。IGF-I以时间依赖性方式诱导IGFBP-3和IGFBP-5蛋白，而相应的mRNA没有增加。IGF-I刺激后，IGFBP-4蛋白水平下降。TGF-β刺激IGFBP-3的mRNA和蛋白，但降低IGFBP-5的mRNA和蛋白。相比之下，与对照组相比，PDGF-BB未能调节IGFBPs。然后测试重组人IGFBP-3（rhIGFBP-3）对IGF-I诱导的HSCs有丝分裂的影响。rhIGFBP-3以剂量依赖性方式抑制IGF-I刺激的DNA合成，在25 nM IGFBP-3时观察到最大效应。由于TGF-β在肝硬化肝组织中高度表达，我们确定在因病毒诱导的慢性活动性肝炎而有活跃纤维增殖反应的患者的肝活检中，IGFBP-3 mRNA表达是否增加。在大多数这些样本中，与正常对照相比，IGFBP-3 mRNA增加。这些发现表明，处于激活表型的人HSCs组成性地产生IGFBPs。IGF-I和TGF-β对IGFBP-3、IGFBP-4和IGFBP-5的表达有不同的调节作用，这反过来可能调节IGF-I在体外和体内的作用。
