Knockout of secretin receptor reduces large cholangiocyte hyperplasia in mice with extrahepatic cholestasis induced by bile duct ligation.
During bile duct ligation (BDL), the growth of large cholangiocytes is regulated by the cyclic adenosine monophosphate (cAMP)/extracellular signal-regulated kinase 1/2 (ERK1/2) pathway and is closely associated with increased secretin receptor (SR) expression. Although it has been suggested that SR modulates cholangiocyte growth, direct evidence for secretin-dependent proliferation is lacking. SR wild-type (WT) (SR(+/+)) or SR knockout (SR(-/-)) mice underwent sham surgery or BDL for 3 or 7 days. We evaluated SR expression, cholangiocyte proliferation, and apoptosis in liver sections and proliferating cell nuclear antigen (PCNA) protein expression and ERK1/2 phosphorylation in purified large cholangiocytes from WT and SR(-/-) BDL mice. Normal WT mice were treated with secretin (2.5 nmoles/kg/day by way of osmotic minipumps for 1 week), and biliary mass was evaluated. Small and large cholangiocytes were used to evaluate the in vitro effect of secretin (100 nM) on proliferation, protein kinase A (PKA) activity, and ERK1/2 phosphorylation. SR expression was also stably knocked down by short hairpin RNA, and basal and secretin-stimulated cAMP levels (a functional index of biliary growth) and proliferation were determined. SR was expressed by large cholangiocytes. Knockout of SR significantly decreased large cholangiocyte growth induced by BDL, which was associated with enhanced apoptosis. PCNA expression and ERK1/2 phosphorylation were decreased in large cholangiocytes from SR(-/-) BDL compared with WT BDL mice. In vivo administration of secretin to normal WT mice increased ductal mass. In vitro, secretin increased proliferation, PKA activity, and ERK1/2 phosphorylation of large cholangiocytes that was blocked by PKA and mitogen-activated protein kinase kinase inhibitors. Stable knockdown of SR expression reduced basal cholangiocyte proliferation. SR is an important trophic regulator sustaining biliary growth.


CONCLUSIONS
The current study provides strong support for the potential use of secretin as a therapy for ductopenic liver diseases.
Glaser
Shannon
S
Scott & White Digestive Disease Research Center, College of Medicine, Temple, TX, USA. sglaser@medicine.tamhsc.edu
Lam
Ian P
IP
Franchitto
Antonio
A
Gaudio
Eugenio
E
Onori
Paolo
P
Chow
Billy K
BK
Wise
Candace
C
Kopriva
Shelley
S
Venter
Julie
J
White
Mellanie
M
Ueno
Yoshiyuki
Y
Dostal
David
D
Carpino
Guido
G
Mancinelli
Romina
R
Butler
Wendy
W
Chiasson
Valorie
V
DeMorrow
Sharon
S
Francis
Heather
H
Alpini
Gianfranco
G
D000818:Animals; D017209:Apoptosis; D001652:Bile Ducts / Q000187:drug effects / Q000473:pathology*; D049109:Cell Proliferation; D001651:Cholestasis, Extrahepatic / Q000150:complications* / Q000235:genetics / Q000473:pathology; D055786:Gene Knockout Techniques; D006965:Hyperplasia / Q000235:genetics / Q000473:pathology; D008099:Liver / Q000187:drug effects / Q000473:pathology*; D008107:Liver Diseases / Q000209:etiology* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009929:Organ Size; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000502:physiology*; D011964:Receptors, Gastrointestinal Hormone / Q000235:genetics / Q000502:physiology*; D012633:Secretin / Q000494:pharmacology
D018809:Proliferating Cell Nuclear Antigen; D043562:Receptors, G-Protein-Coupled; D011964:Receptors, Gastrointestinal Hormone; C029937:secretin receptor; D012633:Secretin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3