Thyroid hormone inhibits biliary growth in bile duct-ligated rats by PLC/IP(3)/Ca(2+)-dependent downregulation of SRC/ERK1/2.
The role of the thyroid hormone agonist 3,3',5 l-tri-iodothyronine (T3) on cholangiocytes is unknown. We evaluated the in vivo and in vitro effects of T3 on cholangiocyte proliferation of bile duct-ligated (BDL) rats. We assessed the expression of alpha(1)-, alpha(2)-, beta(1)-, and beta(2)-thyroid hormone receptors (THRs) by immunohistochemistry in liver sections from normal and BDL rats. BDL rats were treated with T3 (38.4 mug/day) or vehicle for 1 wk. We evaluated 1) biliary mass and apoptosis in liver sections and 2) proliferation in cholangiocytes. Serum-free T3 levels were measured by chemiluminescence. Purified BDL cholangiocytes were treated with 0.2% BSA or T3 (1 muM) in the absence/presence of U-73122 (PLC inhibitor) or BAPTA/AM (intracellular Ca(2+) chelator) before measurement of PCNA protein expression by immunoblots. The in vitro effects of T3 (1 muM) on 1) cAMP, IP(3), and Ca(2+) levels and 2) the phosphorylation of Src Tyr139 and Tyr530 (that, together, regulate Src activity) and ERK1/2 of BDL cholangiocytes were also evaluated. alpha(1)-, alpha(2)-, beta(1)-, and beta(2)-THRs were expressed by bile ducts of normal and BDL rats. In vivo, T3 decreased cholangiocyte proliferation of BDL rats. In vitro, T3 inhibition of PCNA protein expression was blocked by U-73122 and BAPTA/AM. Furthermore, T3 1) increased IP(3) and Ca(2+) levels and 2) decreased Src and ERK1/2 phosphorylation of BDL cholangiocytes. T3 inhibits cholangiocyte proliferation of BDL rats by PLC/IP(3)/Ca(2+)-dependent decreased phosphorylation of Src/ERK1/2. Activation of the intracellular signals triggered by T3 may modulate the excess of cholangiocyte proliferation in liver diseases.
Fava
Giammarco
G
Central Texas Veterans Health Care System, Department of Medicine Temple, Texas 76504, USA.
Ueno
Yoshiyuki
Y
Glaser
Shannon
S
Francis
Heather
H
Demorrow
Sharon
S
Marucci
Luca
L
Marzioni
Marco
M
Benedetti
Antonio
A
Venter
Julie
J
Vaculin
Bradley
B
Vaculin
Shelley
S
Alpini
Gianfranco
G
D000818:Animals; D017209:Apoptosis; D001652:Bile Ducts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D049109:Cell Proliferation; D015536:Down-Regulation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D010766:Phosphorylation; D051381:Rats; D011916:Rats, Inbred F344; D011988:Receptors, Thyroid Hormone / Q000096:biosynthesis; D015398:Signal Transduction; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis*
D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D015544:Inositol 1,4,5-Trisphosphate; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010738:Type C Phospholipases; D002118:Calcium