Insulin-like growth factor-1 isoforms in rat hepatocytes and cholangiocytes and their involvement in protection against cholestatic injury.
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.
Gatto
Manuela
M
Department of Clinical Medicine, Division of Gastroenterology, University of Rome 'La Sapienza', Rome, Italy.
Drudi-Metalli
Veronica
V
Torrice
Alessia
A
Alpini
Gianfranco
G
Cantafora
Alfredo
A
Blotta
Ida
I
Alvaro
Domenico
D
D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D001659:Biliary Tract / Q000166:cytology / Q000378:metabolism*; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D002779:Cholestasis / Q000517:prevention & control*; D017931:DNA Primers; D020868:Gene Silencing; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D007527:Isoenzymes; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I