Gatto Manuela, Drudi-Metalli Veronica, Torrice Alessia, Alpini Gianfranco, Cantafora Alfredo, Blotta Ida, Alvaro Domenico
Department of Clinical Medicine, Division of Gastroenterology, University of Rome 'La Sapienza', Rome, Italy.
Lab Invest. 2008 Sep;88(9):986-94. doi: 10.1038/labinvest.2008.63. Epub 2008 Jul 7.
A 'locally acting' IGF1 (insulin-like growth factor 1) isoform has been recently identified in the skeletal muscle and neural tissues where it accelerates injury repair. No information exist on the expression and function of IGF1 isoforms in the liver. We investigated IGF1 isoforms in rat hepatocytes and cholangiocytes and evaluated their involvement in cell proliferation or damage induced by experimental cholestasis (bile duct ligation, BDL) or hydrophobic bile salts. IGF1 isoforms were analyzed by real-time PCR by using beta-actin as internal reference. In both hepatocytes and cholangiocytes, the 'locally acting' IGF1 isoform (XO6108) and 'circulating' IGF1 isoform (NM_178866) represented respectively 44 and 52% of the total IGF1. Basal mRNAs for both 'locally acting' and 'circulating' IGF1 isoforms were higher (P<0.05) in hepatocytes than cholangiocytes. After BDL for 3 h, the 'locally acting' IGF1 isoform decreased threefold (P<0.05) in hepatocytes but remained stable in cholangiocytes with respect to sham-controls. After 1 week of BDL, hepatocytes displayed a further fivefold decrease of 'locally acting' IGF1 mRNA. In contrast, cholangiocytes showed an eightfold increase of the 'locally acting' IGF1 mRNA. The effect of 3 h of BDL on IGF1 isoforms was reproduced in vitro by incubation with glycochenodeoxycholate (GCDC). The cytotoxic effects (inhibition of proliferation and induction of apoptosis) of GCDC on isolated cholangiocytes were more pronounced after selective silencing (SiRNA) of 'locally acting' than 'circulating' IGF1 isoform. Rat hepatocytes and cholangiocytes express the 'locally acting' IGF1 isoform, which decreased during cell damage and increased during cell proliferation. The 'locally acting' IGF1 was more active than the 'circulating' isoform in protecting cholangiocytes from GCDC-induced cytotoxicity. These findings indicate that, besides muscle and neural tissues, also in liver cells the 'locally acting' IGF1 isoform is important in modulating response to damage.
最近在骨骼肌和神经组织中发现了一种“局部作用”的胰岛素样生长因子1（IGF1）亚型，它能加速损伤修复。目前尚无关于IGF1亚型在肝脏中表达和功能的信息。我们研究了大鼠肝细胞和胆管细胞中的IGF1亚型，并评估了它们在实验性胆汁淤积（胆管结扎，BDL）或疏水性胆盐诱导的细胞增殖或损伤中的作用。以β-肌动蛋白为内参，通过实时PCR分析IGF1亚型。在肝细胞和胆管细胞中，“局部作用”的IGF1亚型（XO6108）和“循环”的IGF1亚型（NM_178866）分别占总IGF1的44%和52%。肝细胞中“局部作用”和“循环”IGF1亚型的基础mRNA水平均高于胆管细胞（P<0.05）。BDL 3小时后，肝细胞中“局部作用”的IGF1亚型减少了三倍（P<0.05），但与假手术对照组相比，胆管细胞中的该亚型保持稳定。BDL 1周后，肝细胞中“局部作用”的IGF1 mRNA进一步下降了五倍。相反，胆管细胞中“局部作用”的IGF1 mRNA增加了八倍。用甘氨鹅去氧胆酸（GCDC）孵育可在体外重现BDL 3小时对IGF1亚型的影响。在选择性沉默“局部作用”的IGF1亚型而非“循环”的IGF1亚型后，GCDC对分离的胆管细胞的细胞毒性作用（抑制增殖和诱导凋亡）更为明显。大鼠肝细胞和胆管细胞表达“局部作用”的IGF1亚型，该亚型在细胞损伤时减少，在细胞增殖时增加。在保护胆管细胞免受GCDC诱导的细胞毒性方面，“局部作用”的IGF1比“循环”的亚型更具活性。这些发现表明，除了肌肉和神经组织外，“局部作用”的IGF1亚型在肝细胞中对调节损伤反应也很重要。
